Why? I like it. I think it works because it adds complexity to their relationship. I think they really care for each other, but it's not easy to be together due to their jobs. I also like it their weird romance/relationship is not the main focus of the show, but it's an important ongoing subplot. The mistake some shows make is when they focus so much on the romantic angst and it's just tiring. Show them working together and with the team and slowly put them back together when they accomplish other goals in their lives.