/s
Edit: I thought you were joking and that the answer was more like printing presses and a lack of an official "standard English" in the 1700s/1800s, but it turns out the answer really was closer to what you said. Noah Webster deliberately decided to make American English diverge from British English when he wrote his dictionary.
Proton makes safer, more private (than, say, Gmail) email a possibility for people who don't have much technical knowledge but who know enough to want to keep their emails out of Google's hands.
If you have both the knowledge and time to run a server, by all means, that can make sense (and can be fun!). It's just not as widely applicable.
The point of ownership is having your mails in your hand, on your iron, anything who can talk IMAPs or even POP is ok for that. For voice/chat etc Matrix or XMPP might be yours, so nobody could decide to ban you or shut the service down. You still depend on a ISP ok, but much less dependencies anyway. That's the point IMVHO.
While thinking that company X is better in privacy terms than company Y is honestly meaningless, you can trust them or not, you don't know what happen on their servers or someone else ones where they actually live on (like using Amazon o Microsoft cloud as a backend).
proton meet is already targeting a really niche set of customers, and you're taking it to another level.