One of the drawbacks of using a custom domain for personal email is you essentially have to pay for it for life, otherwise anyone can just buy your old email address if the domain expires and start receiving mail, resetting accounts... I think some folks don't fully consider this consequence when setting up a fun vanity email address or similar etc, especially now both iCloud and gmail have made it so trivial to link a custom domain.
Conversely, if yahoo/google ever stop offering free email, I'll probably end up paying them much higher prices to keep going for a bit until I can transition.
If either ever stop period, especially one day to the next, FML...
Speaking for myself, the "blast radius" of my email address is some 600+ accounts... (just looking in my password manager). The chances of me sitting down and closing every single one are non-existent. Many won't even have the luxury of having diligently tracked their login accounts in a password manager either.
Just having a family, kids, bills, schools, jobs, credit cards, banks, investments, insurance, shopping etc etc - the number of accounts many of us pick up can easily get into the hundreds.
