I won't debate popularity, but from the standpoint of this healthy hetero guy, I don't find T.S. particularly attractive, which I think is part of what her purpose is on the show. Is it important? No, absolutely not, but that's obviously what the showrunners want—a tough, hawt, experienced street cop that has chemistry with the leading male character. Tough? Yeah, maybe, and I'm fine with that. Hawt? No. PermaSmirk™ put an end to that. Experienced? I suppose. But a big ol' "F" on her chemistry test.
As I said, I don't care whether a detective on a procedural is smokin' hot or plain-Jane.