You could opt out in the US too, required paying a monthly unlisted number fee

And also in the UK when someone tried to issue a reverse look-up CD they were sued by whatever BT was called at the time.

Even from facebook you could opt out. I am mostly sure you can create account without phone number

It might depend on your IP and other factors. I tried to make a new one about a year ago and could not do it without phone verification.

Maybe they'll let you sign up without a phone number via Tor or something though.

It's not just Facebook that requires a phone verification now, I can't even make a Google or Yahoo Japan account without it. At least on these services you can "reuse" previously used numbers by unlinking them, at least a few times. But services like Discord lets you verify with each number once and only once as far as I know.

On the one hand I get that there's a room for abuse by spams, but on the other hand, I really wish I could freely sign up to services.

I have an old Facebook account without a phone number linked to it. Every time I log on they badger me to link a phone number. Recently the field is pre-filled with a phone number I use that I never explicitly gave them...

If it is possible to make a new account without a number I am assuming it is not made easy.

Is that “pre filled” number your browser’s auto fill by chance?

I would be very surprised if it weren't browser prefilled. Although scummy things like that are not unusual when it comes to facebook, maybe they took it from instagram or whatsapp.