Google has most of my email because it has all of yours (2014)
Having your own email/domain isn’t about privacy. Email has become essentially the key to almost everything in modern life. If I lose access to my email I lose access to basically everything I own and it would be a massive hassle to switch emails. Banks, schools, apps, etc. Often times these services won’t even let you change to a new email if you don’t have access to an existing one. Some use email as 2factor. It’s a nightmare. Owning your own domain separately is crucial. Who hosts your email matters less.