a) besides the some bootstrapping nuances you are not forced to have a working phone number to be able to use some resource. It's usually not a problem until... well until it became a problem. Just like for me yesterday when for whatever I tried but I couldn't register a new Google account. There is just no other option than SMS confirmation.
b) there is way less things to change 'for your own convenience', like a quiet removal of any option to pre-pay for Fastmail.
PS oh and Dynadot (which I was happy using for more than 10 years) decided (for my convenience, of course) to change the security mechanism they used for years. Of course I don't remember the answer for the security question and now I forced to never ever migrate from them, because I literally can't.