To OP: it does add significant block to spammers so they may only create 5,000 accounts slowly instead of millions of accounts quickly.
Most email services require a phone number or other email service to sign up if there is anything fishy about your connection/browser, and there can be hundreds of things, even just some specific browser extension installed, or you using the same mobile network IP as a spammer.
And there are services where you can buy a real temporary 4G/5G number (non-VoIP) for a service for less than a dollar per use. Once a number has been used for that service it still has every other X number (thousands) of services it can be used for before it’s retired from the pool. But that does add up after a while if you’re making tens or hundreds of thousands of accounts.
Which is also why most services that use phone number for user verification ban VoIP numbers, making this basically useless
To OP: it does add significant block to spammers so they may only create 5,000 accounts slowly instead of millions of accounts quickly.
Most email services require a phone number or other email service to sign up if there is anything fishy about your connection/browser, and there can be hundreds of things, even just some specific browser extension installed, or you using the same mobile network IP as a spammer.
And there are services where you can buy a real temporary 4G/5G number (non-VoIP) for a service for less than a dollar per use. Once a number has been used for that service it still has every other X number (thousands) of services it can be used for before it’s retired from the pool. But that does add up after a while if you’re making tens or hundreds of thousands of accounts.