The only reason he asks questions no one else asks, is because he's the only guy interviewing porn stars and asking them if they like anal sex.
You think so, huh? When someone famous comes out with a new movie or whatever and is doing the rounds on all the tv & radio shows, do the following:
1) Tape the interview they have with Letterman, Leno, and Conan.
2) Tape the interview they have with Howard Stern.
After you've taped them all, listen to them back-to-back.
For case 1, you'll find that they're cookie cutter interviews. They ask the same questions, and the people give dumb and boring answers. "Yes, it was great working with him because he's just a genius and ..." ... ugh ... Usually they tell the same anecdotes on each show, too. These shows are for promotion first, "funny" anecdotes second, and interviewing third.
For case 2, you'll find that the interviews are almost always entertaining and interesting because Howard focuses on the interview first and foremost. Howard doesn't
ask the cookie-cutter questions, and when the guest tries to tell their 'funny' anecdote that they've told a million times before, Howard will always cut them off and ask an interesting question. When he's not getting a good interview, he goes to great lengths to create a good interview and that's usually where the sex-oriented questions come in, and that's usually the topic that makes people uncomfortable about the show. But when you listen to enough interviews, you'll discover that it's part of his overall interviewing style: a carefully crafted sequence of questions and comments that often brilliantly manipulate the interviewee into providing an interesting segment on the show.
There are other good interviewers out there who do have interesting interviews without resorting to 'smut', as people call it, but nobody can force a good interview from someone like Howard can.