The owner has the choice between iOS and Android. Why should Apple change their policies (and lose revenue) if the majority of users appear to be sufficiently happy with those restrictions (otherwise they wouldn't buy iOS devices)?
Also, the idea that users understand these issues and are passing judgment on them when they buy an iPhone doesn't seem realistic for the majority of iPhone owners. If you walked around polling iPhone users about this issue anywhere besides Silicon Valley, the most common answer would probably be "What?" And that's ignoring the fact that someone might object to this but still buy an iPhone for unrelated reasons. So even if their dollars could act as moral validation, I don't think it's reasonable to say they do in practice.
Kind of like having fire exits benefits users even if people don't pick retailers based on their existence.
So, the choice is largely:
some freedom ^ (privacy | long-term updates)
Freedom, privacy, and long-term updates are all important to me, so there is no real choice.
You say grownups I hear that some are too weak willed to stand up for their rights.
Money can still be made through app stores (exclusivity is not needed - I'm sure the Play Store is still hugely profitable despite sideloading), from hardware sales, from subscription services, from licensing software to OEMs, and more.
What we're seeing is that companies like Google, Amazon, Apple, and Microsoft are not content to make a lot of money while still keeping some respect for the user. They realize that even more money can be made screwing over the user. This really causes harm to society, as a lot of people realize they're being screwed but feel like they have no choice or agency in the matter. In my opinion, this is a good example of why capitalism and the free market are not ultimate goods in themselves but are rather a means to an end, and can certainly be used for evil purposes.