I absolutely love this.

It's not an accident. They're not stupid. It is intentional. They want your personal information. Most of your personal information is tied to your email but it's easy enough to spin up an alias to sign in with. Requiring a phone number ensures that they know exactly who you are and can buy/sell/use your data accordingly. They also know what a giant pain in the dick it is to change your phone number, especially when you need it for these security checks. They also know sales conversion rates are much higher if they can get you on the phone. So yeah, they're not going to stop doing that.

I have absolutely no need for my phone number, nor do I use it for anything that I couldn't use a voice app for. Just get rid of them altogether.