The reason for my want/need for combat logs is very simple. I raid. And I raid competitively. Right now I am in an 8 man that is starting Nightmare pretty soon and I would perfer if we went into 16 mans. The reason why my 8 man is so far ahead after its first raid week is because I trust everyone in there due to playing with them previously, or they are trusted friends of others.
Swapping to 16 man though, I do not know the 8 other players and they will have to be recruited from the general public. There is always "THAT" guy that is dead weight and worthless in a raiding environment. Even though he may be the nicest guy in the world he can't do his job so he wastes the time of 15 other people for hours on end. This is where combat logs are nessessary to see why he is dying, why his damage is so low, why other people are dying if hes a healer, ect ect. Any competitive player needs a combat log to answer these questions.
So people who say they don't want combat logs or anything, you are probably "THAT" guy. Which is fine. I will be nice to you and respectful to you but no, I really don't want to play with you. If its possible for me to help you, then I will, but I can't with out logs of any type.