[Johnny555]

what does self-hosting email accomplish in reality

Well, for one thing it prevents Google from building a profile of my online shopping behavior based on my email receipts. Also avoids them knowing every time I go on a trip based on booking confirmation emails.

Like most people, I'm not trying to hide from the government.

[MichaelVangard]

Using a 3rd party email host that isn't Google has the same effect with a lot less effort. I switched to FastMail for this reason, even if Google claims not to scan paid Gmail accounts for marketing purposes.