You sign up for a health plan using healthplan@example.com. Great, until you need to send them a document. You send it from myrealaddress@example.com, and they write back and say hey, that’s not the account on file, etc.
So now you have to set up healthplan@example.com, configure it in your mail client, etc. And now you have this long list of special addresses to remember to have to send from, depending on the situation.
Email is already something I loathe. Why would I make it harder on myself?