Moderators are generally pretty careful about not using moderator powers, like handling flags or deleting comments, on posts where we have a vested interest. Protecting a question, like closing, reopening, or editing, is a reputation-based privilege not restricted to moderators. The same people who can protect a question can also unprotect it, even if it was protected by a moderator.
Questions are usually protected when they are attracting low-quality answers or spam. In fact, the system (as the Community user) automatically protects questions that meet a certain threshold for this. So long as protection isn't used egregiously and people aren't fighting protect/unprotect wars, I don't see a problem. And if, in particular, the asker of a question protects it, arguably he's the one who's harmed the most by potentially cutting off answers he presumably wanted to see.
Sometimes the circumstances that led to a protection don't persist over time. Maybe a question was on the Hot Network Questions list and attracting negative attention, so it was protected, but then time passed and this is no longer a concern. Feel free to unprotect if you have the privilege, or raise the issue on meta or in chat. We don't have good tools for monitoring protection, so if you see an older protected question and wonder why it wasn't unprotected already, chances are the answer is "nobody noticed".