Gitlab now requires phone number/credit card verification
Looks like gitlab now requires account verification for new accounts in addition to email. Either phone number or credit card.
This applies both to accounts created with a working email or by logging in using your github account. You can't even verify your email until you go through step 1.
I don't know when this started, but at least for the last month or two judging from these posts in the forums.
Because it's a decent competitor to the GitHub monopoly. It also has a few unique features when compared to it. Just guessing why OP uses it though (many people do)