App support and camera quality I can understand more. I'm on a Linux phone using Phosh (FLX1s), and there's Android app compatibility, but it is a little rough (and of course things that rely on Play Integrity won't work). I've managed to avoid tying myself to anything that requires Google for now, but I acknowledge that I'm lucky there.
It can be a lifestyle difference.
I personally don't being my wallet in most daily trips, have no use of it. I used to stick a credit card in my phone case but also got rid of it as more stores reliably offered wireless and QR code payments.
Mind you this comes with a specific environment I don't expect everyone to live in or long for, I'm just explaining.
IMO it's not a matter of tap to pay and camera quality, rather a matter of whole system paradigm. Having millions of disconnected services in the "do one thing and do it right" spirit and using text based communication and hundreds of python and shell scripts is relatively maintainable and relatively easy to use, but very inefficient when it comes to CPU cycles - and on a handheld every cycle counts.
And of course every app is optimized for desktops/laptops... but I guess that's a chicken-or-egg problem: once there is a working distro, there will be apps too. And once there will be apps to use, there will be a working distro. Maybe.
If I read correctly, you identified the lack of smarthpone-level apps and distro as the limiting factor. In my opinion, the lack of sufficiently powerful but still open hardware is what we miss. Mainline linux with proper hardware support is pretty good but not complete on the Snapdragon 845, a 9 y/o platform. Anything newer? Nearly impossible without some android-specific layers (such as libhybris in the case of Droidian). Currently mid-high level hardware with PinePhone-like openness would probably let Phosh (and Plasma-Mobile, SXMO etc.) distros strive. The smart features, as in the apps, are mostly there.
My experience today is that I have all the applications I need daily, and the odd ones I don't have natively I can run in Waydroid. There are currently some limitations when it comes to access to hardware from within the container, but nothing that couldn't be overcome with some moderate effort. The only real blocker is remote attestation, but I see it as a threat to the whole fabric of society, not just Linux phones, and it should be opposed regardless of platform one uses.
I don't really get tap-to-pay. I never thought it's something I want or need to have on my phone (which doesn't even have NFC, though it could be added as an extension). I just use a card. I get it that it may be slightly more convenient, but definitely not worth changing the OS over, let alone giving others control over my phone. That said, I have full access to my bank account from my phone anyway. Practically everything except TOTP payments (Blik) can be done from the Web (and with Epiphany's webapps it's just there as an app to launch), and Blik can be used from the Android app in Waydroid. Frankly, if I couldn't access the bank from my phone I would rather change the bank than the phone, and would make sure to let the customer service know very clearly why I'm doing that.
And when it comes to camera quality, matching the state-of-the-art overprocessed mess would be hard, but having played with camera processing a lot recently I can say that perfectly adequate quality is absolutely well within the reach (if not there already for daylight photos). I only researched absolute basics of photo processing and implemented some essential stuff while completely ignoring others and I'm already quite happy with the photos I get (https://social.librem.one/@dos/tagged/shotonlibrem5) and there's enormous room for improvement still that only needs someone who knows what they're doing to sit down and implement things that are missing. Some of that stuff is already happening around libcamera as more people get involved there thanks to laptops with webcams that also need similar software handling. The particular phone I'm using doesn't have hardware video encoder (only a decoder) so video recording will stay low res there forever unless limited to short clips, but it's not a limitation inherent to the platform, just to this specific device.
I have briefly carried an Android device as a secondary phone some 10 years ago out of necessity (N900 was starting to get too old to handle the Web and Librem 5 did not exist yet) and it felt quite miserable, it seemed like an appliance rather than a personal computing device despite of equipping it with microG, F-Droid, rooting it etc. When you're used to being able to script a simple thing right on your phone using whatever technology you already feel comfortable with, it's hard to give it up. Just try to patch a simple thing from the system's core on an Android phone - yes, it's possible if you're really determined, spend a lot of time on it and don't mind attestation issues, but I can do that with dpkg-buildpackage on my phone's screen within minutes, send a patch upstream and have it actually merged in time it would take my laptop to produce an Android image. I may not exercise this ability a lot in my daily use, but having such possibility is incredibly empowering. I can't see Android becoming competitive there, quite the contrary ;) The only actual obstacle I see on the path to growth is the threat of remote attestation gaining widespread use and this affects any existing or future platform from outside the duopoly, not just GNU/Linux in particular, and I believe this still isn't a lost game.