I find it strange too, though that may be because of the type of locations I stay. I don't seen any reason for customer loyalty to a single booking site. There is very little friction to just use the hotels own booking sites. For each town I stay in there is usually two or three hotels to choose from that have online booking (occasionally I have to make a phone call to book since there are no hotels with online booking.) From those two or three, I sort them by price, and work from the cheapest to the most expensive until I find the cheapest that I think will provide what I want, and book using that hotels site. Occasionally it is booking.com, but more often than not, it is the Motel 6 corporate site or the Comfort Inn corporate site or similar.

I also never look at reviews since my experience has found that reviews are useless to me. I think reviewers tend to care about things I don't, and have had excellent experiences at places with generally bad reviews.