I do it because I got tired of my email changing every time I move or the ISP changes hands.
It's also good experience incase you need to be a server admin.
Running your own email server is completely unnecessary for that. All you need is to have your own domain name.
I've had my own domain for ... checks ...
Domain Name: HOULT.ORG
Creation Date: 2000-05-10T10:11:35Z
Registry Expiry Date: 2029-05-10T10:11:35Z
So actually that's 21 years ago *today*. And I keep ahead on the expiry date -- I prepaid it up to 10 years a year ago.
Over the years that's been hosted in a number of places.
- I've had my own Linux mail server at home
- a friend in the USA with a hosted box at rackspace.com offered me free hosting in exchange for some light admin duties and "his paying customers not noticing whatever I did on the box".
- once gmail started and was clearly the best webmail app I used a .forward from the rackspace machine. That only strengthened once they got a great iOS native app.
- sadly my friend died a few years ago. I'm now using a commercial hosting service, but just having them forward everything to gmail. Some of my other family members are using webmail and pop/imap directly on the current commercial provider.
- I regularly download and archive everything from gmail
For the moment, and for quite a few years now, I'm happy with physically reading and sending my mail via gmail. But I don't depend on them in any way. Physically, all my mail goes first to a server that I have at least some management control over before being forwarded to gmail.
If either google or the web hosting company disappear or change their T&Cs in an annoying way I can pack up and go elsewhere with a few minutes of work. No one who sends me email will notice a thing.