That is only one important aspect. It's also provider-independent (as long as you own the domain, that is true) and is, by nature, decentralised. (Like really decentralised, even by redundancy provaded by MX record priority in DNS.)
When companies have kindly sent me their entire customer list (by using CC in place of BCC) I see there are very few domains in it outside of the major free email providers, and those that remain are mostly for their work or small business. A personal or family domain is very rare.
You can renew a domain for ten years in advance and easily transfer between registrars (and email providers, I use Fastmail), so it's a lot more reliable for the (very) long term than a third-party service.