When I bought my domain, it was before Gmail was as ubiquitous as it is today. My email was hosted by a mom and pop ISP. Then I moved to Gmail and later to Fastmail.
Having my own domain is inexpensive, fun, and lets me maintain email portability over time. Namecheap is a good, easy registrar. I moved to them a while back and was impressed at their documentation and help during that domain transfer.
I think that, similar to cell phone numbers, people get very attached to these contact points and changing them creates anxiety. I happen to have changed both email address and phone number (after five years) recently and I think it makes sense to do once in a while. Otherwise these things become seemingly permenant identifiers and I have enough of those already (:
Me, my spouse, and my teenaged kid all have our own domains. They're all hosted at Fastmail under a group account and we all can have as many additional addresses tied to our regular accounts as we want.
It does cost a bit more ($15/year/domain at Gandi, my preferred registrar) than just paying Fastmail directly and using one of their domains or sticking with the costs-no-money Gmail offering but it's been worth it in unexpected ways. My kid, for instance, is following in the "family business footsteps" and doing IT work for small clients. Since he had his own domain, he can have prospective clients e-mail him at "consulting@hisdomain.tld" My spouse uses a bazillion aliases for spam and inbound e-mail filtering without tipping off the spammers to the underlying e-mail address by having to use the + notation.
Someday, when my kid strikes out fully on his own, he'll be able to take his domain with him to wherever he wants (even host it on Gmail, if he prefers) without losing any of his addresses or other contacts. My domain has been around for over two decades and has been hosted in easily 20 different places, but my main e-mail address has remained the same.
It's nice and worth the money.
Seriously, migration is as easy as pointing your MX records to them and running their import tool. It takes ten minutes (I thought switching off Gmail would take ages, but no, literal ten minutes).
I think the problem here is that this is a Gmail-specific, non-standard feature, meaning there is no specification that allows to implement this in a reliable, cross-client way.
However, Fastmail is working on something similar with JMAP.
I found this earlier HN comment to be really interesting: https://news.ycombinator.com/item?id=16372835
They are! [1]
"It really is coming in JMAP! Come along to IETF in London to have a play, or I'll be pushing out links to updated JMAP Proxy in the next couple of weeks and you can play with it there :)"
Once they've got JMAP nailed down, they'd just need to support Gmail's native API [2] for retrieving rich message data for their import process.
I used to use it for awhile. Then I got some AWS credit so I setup Amazon Work Mail.
runbox.com (cheapest for >1 user)
rackspace.com/email-hosting
zoho.com/mail
www.gandi.net (free w/ domain registration)