I think the question becomes, are people using Debian in large part because of those principles, or in spite of the inconveniences that come with them because of other benefits (e.g. it's a fairly well-maintained, stable Linux distribution, that very aggressively believes if something worked on 11.0 it better still work on 11.9)?
If we look at popcon[1], it currently says 11.84% of users who opted into popcon regularly use the "firmware-misc-nonfree" package, along with 9.57% for the realtek package, 8.76% for the modern Intel wifi firmware package (iwlwifi), and 7.07% for firmware-amd-graphics.
I can't claim that's a statistically significant percentage of Debian users, I don't have that data, but of the ones who volunteered their information, even assuming perfect overlap, a not insignificant number of users are happily opting into the "not officially Debian, we swear" portion of the world.
Speaking as someone who is part of this "significant percentage of Debian users", I'd like to point out that opting in is the key part in the phrase "happily opting into".
I've made a conscious choice to install the non free packages. I'm quite happy I had that choice, but I'm even happier that they weren't forced on me.
I certainly hope nobody will point to me and say "look here, non-free should obviously be the default!"
I don't think anyone is proposing removing the ability to not install with nonfree packages, merely whether the default should remain as it is.
Personally, while I would prefer to be able to change and replace the software running on the tiny computers that make up a modern system, focusing on the distinction between "the vendor shipped it on a flash chip so we don't have to think about it" and "we need to load it at runtime" seemed a bit like spending too much effort on too little reward, to me - if we convince the manufacturer to up the cost by a few cents to hide the firmware blob from us, is that really a victory for Free Software, simply because we don't have to think about it? (Particularly if it sometimes results in never having ready access to a mechanism to replace the firmware blob, should someone sufficiently motivated either convince them to Free it or develop a replacement?)
It's great whenever someone develops replacements bits or, even more rarely, convinces a company to release their firmware bits permissively, but without a list of examples of Debian's stance changing the policies of other organizations, I think it's not that effective a tool for changing behavior in this case, and instead primarily inconveniences people who want to use Debian.
Whether they end up changing the default behavior or not, people in this thread replying "wait, there are firmware-bundled images?" makes me think Debian should either stop making them or stop making them so unintuitive to discover.
I'm a Debian desktop user for both principles and stability. I try to use free software only, but I use the non-free ISO when installing onto a new machine, because I need it to work in the first place.
The Web has plenty of tutorials explaining the installation process and the difference between the official ISO and the non-free ISO, even though I would love a better Debian Wiki.
Maybe it's a bit of gatekeeping, but popularity by itself shouldn't be the goal for Debian. You don't know how to install Debian, you don't want to search for a tutorial first, you won't let someone more knowledgeable to help you? Well, I believe this is not the best place for you, you'll face worse things on the road if you keep using Linux.
It's not that simple. Debian is the way it is because of its principles. You can't remove the principles and keep everything else working the same way.
(But, of course, this isn't an uncompromisable principle, as evidenced by the existence of the non-free repository. Packaging basic firmware on the same image as the rest of the system isn't the unthinkable action that people are talking about, but silently running them would be.)
Debian is a great project I know. But the comment that they only use debian for its principals directly suggests they would use something else if principals were not considered. Suggesting the other distros are better for their uses. Anecdotally I don't think I have ever seen a debian desktop user, and I wouldn't pick it for desktop either because they don't make it easy to get everything working like other distros do where you check a box on install to include the proprietary bits.
I'm a Debian desktop user not because of principles - I use proprietary blobs including Nvidia's drivers - but just because it's what works best of the distros I know.
I've been burned a couple times too many on Ubuntu's regressions. They'll ship a newer version of a package that breaks some use case which isn't super common but not super obscure either, and then I have to figure out what broke. I've stopped trusting Ubuntu's packages so I don't use Mint either even though I like the distro.
Debian continues to impress me with its stability. I run the testing branch at home and breakage is still extremely rare. Yes, there's things that Debian makes harder to set up, and running Debian means you basically resign yourself to running a userspace that's 1+ year old, but the overall experience just works better in my experience.
Maybe I should give Fedora a serious try one day. I haven't properly used any Red Hat based desktop since Mandrake but I did like CentOS a lot for servers.
Have been using Debian as my daily driver for 5+ years on both desktops and laptops. No issues at all though I did spend some time on gnome shell to get it closer to what I prefer (multiple desktops, alt-tab behaviour, etc)
Another Debian desktop user here. Ages ago I tried a lot of different distros, but none of them just stay running like Debian. My computers are for using, not for fixing random errors at inconvenient times.
The installation process, that I have to run when a local disk eventually fails is insignificant compared to constantly fixing shit. (And yes, it's not a nice process - even worse because every time I run it, it changed.)
I use Debian on desktop, because it's the most problem-free distro I've used. Once something works, it usually stays this way with no effort on my part. Ubuntu was the opposite for me, which is weird given how it's a Debian derivative.
I don't care about FOSS, so the principles are not a motivation for me.
I have no idea but it stayed through many staff changes. The university I went to next (U. Bordeaux, ~50k students) 's comp. sci. department computers were also running Debian iirc.
And many of the other top Linux distributions are Debian derivatives which both participate in the community and provide the alternate experience.
Upholding its principles is the way Debian distinguishes itself. If you don't like it, use Mint or something.