Different person here, but: literally anything. I don't have "anything to hide," but I don't trust the company's judgment (or, more specifically, that of every possible "company representative." It only takes one to make something a federal fucking issue.)

If I do a google search for "cake toppers for lesbian wedding" while my code's compiling, that's morally fine. But if a bored "company representative" decides to take offense to that, now it's a whole goddamn situation that I have to deal with.

Or if I'm on Stack Overflow to copy&paste, and one of the "Hot Network Questions" in the sidebar has an "offensive" phrase in it, is it going to trip their automated flagging criteria?