With phone numbers, you can move from one carrier to another, while retaining your number. This helps with competition.

We need the same for email.

Sure, it may not work with the ancillary services, but keeping your email address would solve a lot of issues.

I mean, you can do that already, you use your own domain name and can then change email providers at will, in theory.

But maybe you logged in to your domain registrar through google oauth. If your google account is locked you can't now get into your domain's settings to change your MX records.

The real problem isn't the email address itself, it's all the access that google owns on your behalf. Lose access to Google, lose access to everything.