That's really interesting and definitely something worth trying. I wonder how the effectiveness of email changes with the goals for the user (play solitaire vs pay for a subscription, etc).
I think age plays also a role. I have met various young people who have't entered the "working world" yet, that only have an email address because they needed one for registration and to recieve some school related information. But it is percieved as something completely arcaic and they never use it for anything else nor check it regularly. All communication is via messangers or social media.
On the other hand also elderly are or could be moving in this directions. E.g. my mother getting an iPad and apps like Whatsapp have completly changed "computers" for her. From, being mostly a chore that you have to use, to something really useful for getting information and to stay in touch with relatives in other countries
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.
On the other hand also elderly are or could be moving in this directions. E.g. my mother getting an iPad and apps like Whatsapp have completly changed "computers" for her. From, being mostly a chore that you have to use, to something really useful for getting information and to stay in touch with relatives in other countries