In my experience the overwhelming majority of services permit me to change my email address.

Of course. But I have hundreds of user accounts, as probably many people do. I would not enjoy changing all those email addresses.

wouldnt this be the case for any vendor you choose?

Indeed. But some are easier to change than others. I switched my e-mail provider, and it took all of five minutes to launch the copy of my data. Since I kept the same domain, everyone sending me e-mails didn't notice anything.

With Apple's approach, I'd have to go through each account and move it from something@icloud to something@new-domain.

However, for people who don't want to mess around with custom domain names and e-mail providers, apple's approach is very practical. You just need to tell it to "hide your email" when you register somewhere and you're good to go.

yes