In the relatively early days of Expedia, I had a major travel headache because the airline and Expedia were pointing fingers at each other, each saying I needed to deal with the other one to fix the problem (which was not of my doing in the first place - the airline changed the schedule, making my connection impossible). In addition to the reasons I described in my first comment (not trusting that I am seeing all of the options), this is the other thing that puts me off of booking through third-parties. The benefits of booking through someone other than the direct provider need to be huge before I will consider it, and they never are with these travel planning sites.