Most of us will probably move ISP etc., at some time or several times, thus losing our email address(es).
I have my own domain. Thus when I change ISPs (and I use several, at once, for different services) the email address comes with me. Last time I switched hosting providers there was zero downtime and zero lost emails.
Yes, it costs a little more than the "free" email addresses from ISPs and webmail outfits, but sometimes you get what you pay for.