It is related.

You can't easily run your own mail server because the hurdles you have to overcome to not land in gmails (outlook, etc.) spam folder - or even get delivered at all. DKIM, SPOF, a good IP range.

Then your server itself will be exposed to spam and might make it a lot less fun to use.

The big ones are not playing nice with smaller ones because of spam.

I have a couple of dedicated servers in colocation and run my own email server. It's taken more than two years of having all recipients clicking "not spam" and applying to anti-blacklists, ensuring DKIM,SSL Et cetera to actually obtain a decent success rate.

Google, Microsoft really are the destroyers of the internet.

That is so true, but for gmail/hotmail try that:

Gmail:

https://support.google.com/mail/answer/81126?hl=en

Hotmail (register as sender):

https://sender.office.com/

And a good spamtest:

https://www.mail-tester.com/