Well, I enjoyed using the “cached images only” mode in Opera as recently as 2007 on a pay-per-minute 56K dial-up connection that was more like 28K due to the crappy cheap modem. (It wasn’t impossible to get broadband, but nobody felt it was important enough to bother until the last couple of years, and then it took some time to actually get around to it.) The relief at seeing that the JPEG you just commanded to load turned out to be progressive (not that I knew how it worked) was visceral, and the hate towards people making GIF buttons with no alt-text practically unbounded. Uncompressed images were beyond the limit of practicality.