Because it would be very difficult for carriers to co-opt entities like Netflix into nonstandard schemes if there were a lot of competition. You hinted at it i

Because it would be very difficult for carriers to co-opt entities like Netflix into nonstandard schemes if there were a lot of competition. You hinted at it in your comment: "the large players started to talk about colluding" Only a when there are a 'small number of large players' is this kind of collusion possible. When there is a lot of competition, the entire layer of the value chain becomes weaker. It's a problem because they control a scarce resource: the airwaves, and also a kind of scarce resource: access rights for fibre etc..