Yes, I've noticed people are saying that and they are idiots. I have no idea how it could be anything other than great for both their careers and their general adjustment as people to have a loving, kind, supportive relationship with each other. Haven't they seen how damn happy those two always look? And if it isn't harming Lleyton's career I have no idea why it would harm Kim's (in fact hanging around such a professional success-oriented bunch as Lleyton's team might even be a good thing for her!).
Mind you, people have criticised Lleyton for travelling with his mate Hayden and his parents too so maybe they are jealous that they don't have people that love them that much.
I think it's normal for well adjusted young people to have friends and boyfriends (and parents!) and why should K & L miss out just because they are tennis pros?