Each of these platforms' value propositions from earlier days was that some day it'd profit from its own controlled ecosystem. This is how they got investment. Apple and Nintendo in particular each held out a long time protecting the brand. There'd be no point in doing that if you're forced to support the competition anyway.
And in each of these markets, users have other options if they want full hardware control. Clearly it wasn't a priority for many of them.
There's a long runway from "early market" to "total domination" to make money for investors. Nobody is shutting down the ability of limited or emerging markets to extract value, but once you reach Apple's size it's an entirely different story.
The runway is less than one human generation, or less than a home mortgage period. Some of these ventures are unprofitable for a decade. If an investor isn't thinking domination early on, they're thinking of getting it to the point where another investor would think that.
And in each of these markets, users have other options if they want full hardware control. Clearly it wasn't a priority for many of them.