I agree in many cases, but two cases in which I book through the third-party sites: 1. For hotels, where the hotel itself doesn't actually have an online-booki

I agree in many cases, but two cases in which I book through the third-party sites: 1. For hotels, where the hotel itself doesn't actually have an online-booking system. Not very common in the U.S., but common among smaller hotels in Europe. Often a third party (most often booking.com) is the only way to book these hotels online. 2. For flights, where Orbitz or Expedia are able to put together a multi-airline itinerary that I can't get those airlines' own sites to return. The last time I used Orbitz was for this reason: it was able to come up with a round-trip ATL-CPH with Delta one way and KLM the other way, with a good price and times that were convenient for me. The fare rules work because they're partner airlines (so it ends up billed as a round-trip, not two one-ways), but I couldn't manage to get either the KLM or Delta websites to offer me that combination, despite quite a bit of fiddling.