How is you private life have way less data then you public life?
Email accounts have waaaaayy more information about you than a public social media account. I can find out your private thoughts, the things you buy, who you owe money too, your social graph, tons and tons of data. I can find out way more about than from some comments on a nerd forum.
If an email admin looks into your private correspondence your first thought is to get the hell out of his servers, whereas if a mastodon admin constantly monitors public posts from your and other instances then it doesn't seem like a big deal