It's always going to be optional. It's their solution for high-risk users (think: journalists, whistleblowers, and similar), it's not meant to be for everyone.
Disclaimer: No Google affiliation, but I've tested the program a long time ago before it was available to everyone.
Or people with bitcoin wallets, of which I assume there's going to be more and more.
I don't know about it being so much a hardware performance issue, rather than a software optimization issue. Personally, I don't think I need much performance, but I have had issues unlocking my Pinephone because the lockscreen seems to have a hard time keeping track of my finger as I slide it or press the keypad buttons. I've also had a number of kernel panics in the few times that I've used it (I got it just recently).
For the Pinephone to be my daily driver I just need to be able to run Whatsapp on it (so run an Android emulator with access to the SIM card, I imagine; haven't tried) and take real 5MP images. That's all I really need to switch the SIM card and leave my Android phone at home. It can even drop calls and I won't really care (not that it does; I haven't tried).
EDIT: I see I misread a bit and thought you meant its low performance prevented its use as a daily driver. I don't think it makes sense for linux phones to be offered with more expensive hardware until the software catches up to enable their use as daily drivers for more people. I think we're at a stage where the buyers are primarily people that are looking to possibly contribute to the software to get it to that point. Being a cheap phone is important for that.
You can then use a bridge to connect it to Matrix and chat using Whatsapp from any Matrix client.
I can't see it going away. Google uses it to fend off monopoly accusations, viz you aren't locked in, you can always use another app store. Apple doesn't, and they are in a much more threatening territory when it comes to anti-trust law suites against their app store because of it. https://www.cnbc.com/2020/10/06/house-antitrust-subcommittee...
Google has far worse anti-trust problems than Apple in general because they own 80% of some markets, and is being reminded of it repeatedly by ongoing law suites being brought in various countries. https://www.vox.com/recode/2020/12/16/22179085/google-antitr... But for Google Play they have a free pass, and I don't think they aren't likely to give it up any time soon.
I have a PinePhone but it is not yet ready as a daily driver, and also the difference in hardware performance between my Android phone (which I bought this year) and PinePhone (or even Librem) is abismal. I wish there was at least one (or many) linux phone ready to be a daily driver and with hardware comparable to modern Android phones (or iPhones), but unfortunately that is not yet the case, although the community has made a massive effort this year to advance the state of linux on phones, at least for PinePhone...
I use a MacBook for work and same thing, almost all the apps I have I installed using homebrew (and the UI apps, with brew cask)
EDIT: I see that, at least for now, it's optional and you can un-enroll, which is good.