To use your example, when I rent an airbnb, yes I absolutely want to know how much Airbnb is pocketing. Airbnb happily discloses this as an itemised "Service Fee", and they charge hosts a fair 3% fee to cover payments processing.
When I hire a cleaner on Thumbtack, I absolutely want to know how much the cleaner is paid. I want to make sure everyone is earning a liveable wage.
And when I order something through a delivery app, I absolutely want to know how much the restaurant is paid.