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).
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
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.
It will give them the cookie again if they re-visit from any IP they've previously used.
It also re-gives them the cookie if they try to pay again with the same credit card.
Support just tells people to try to resubscribe if their subscription has 'vanished' - but it seems to happen to very few customers.
You're giving anyone on CGNat or even the same coffee shop access to your customers account.