> one of the few privacy-friendly options

almost certainly implies it's not a technical hurdle that they're facing. Plus, purchasing would require giving Google payment details, which would necessarily include billing address, and now it's tied to your phone. I could very easily imagine that giving a lot of folks a lot of heartburn

Huh? Try it, since like ten years it requires validating the account with a phone number, which in many countries requires going through government verification. That alone takes a while to set up if you want a new account that isn't linked to other things already. It's not a quick as generating a new password in your password manager and coming up with a non-taken username anymore

You also can't log into this app specifically, it will tie all apps on your device to this one account. Nobody should be doing this, it's like logging into the Chrome browser and tying all pages that have any sort of google service on it (embedded map, youtube, analytics, ads) to the phone number and thus identity you signed up with