I think a big part of the point is to compete on search (aggregate search like travel sites especially) with the company's competitors. The first company to start, say, charging for a carry-on realizes that they are forcing everyone to copy that, but for a while they'll have an advantage and make more profit. Any business leader doing this first is trying to dishonestly game the system. The others are just doing what they now have to do to keep the playing field level.
On aggregating vacation rental sites, the owners that choose not to do this (at least on sites like VRBO) can add "no service or management costs" to their listings, or maybe "no hidden costs", but it is not very effective because if you are charging $225 and the customer is searching in the range $100 - $200, you loose and the person advertising a $199.00/night charge (with management fee added later) wins.