I've always looked at Leon as the type of interviewer you can mold to fit any need. He's bland on the outside, and I think that's why he works perfectly with the "out there" characters. He's basically the straight man to the fantastical features of whoever he's paired with. With Doe, he's a scaredy cat. With someone like Mikey, he can be the friend that chills with you on the couch eating tacos.
These characters are all really only as good as you make them (you being generalized).
Fair enough. However, I still think there's nothing the interviewer could do that a well written NPC cannot do better. I'm never going to do an interview for an RP. Ever. For the reasons I stated earlier, it's something literally anyone else can do. As for hanging around the interviewers "outside of work".... Theron has no reason to hang out with Leon in a non-interviewing capacity when he has all the misfits to play video games or D&D with. No reason to hang around Stacy since he's spoken for. Klamor maybe could sit in on a D&D session, but I already have two edgy NPC's so there's no reason to use him.
It may just be the story-teller in me who would rather see character development. NPC's can develop alongside the wrestler they are NPC's of, whereas the interviewers are always just gonna be interviewers.