Off the top of my head, a short list of advantages I like:
- someone that will take my side in disputes
- being able to book multiple hotels on one account, in the same place
- cards in wallet in my iphone
- knowing exactly what I'll get
- avoiding misunderstandings that might arise when having to book orally (i.e. wrong number of rooms, wrong number of people, ...)
And that's beyond the superpowerful search, which is kind of immoral to use without giving them the referral fee.