One of the further reason to praise Competition Law.
Expedia and Booking deployed T&Cs which demanded their hotels to provide the lowest price ever only on their respective platforms. This would imply that a given hotel had to offer a higher price even on its own website. Furthermore, this would impede the hotel from being hosted on another platform, since a higher price would hardly be feasible.
The EU Competition authority stepped in in 2014 and demanded such companies to ease their T&Cs which indeeed take place but was not made known to 50% of the hotels in Europe (40% in the NL).