He does mention, somewhat off-handedly, that the lack of email makes password recovery harder. (Presumably impossible without some other communications channel like a phone number.)
And you really need to be able to recover account access for a paid subscription. It's probably also reasonable to assume that if someone is going to give you a credit card number and address, they're probably OK with giving you an email.
This is pretty clever, but people might get double billed if they accidentally try to confirm their account with a different card than they used to sign up.
In my case, customers don't have any data on the account - it's simply a bit saying 'has paid for premium?'. And if I end up giving premium to a few people who didn't pay it isn't an issue. The sign-up friction of needing an email address is greater.
And you really need to be able to recover account access for a paid subscription. It's probably also reasonable to assume that if someone is going to give you a credit card number and address, they're probably OK with giving you an email.