For a cab company, I want a large fleet of cabs, so that I can get the closest one fast. I dont need huge levels of trust in my cab driver. Get me where I want to go, dont kill me in the process, dont rob me.
For a cleaning company, I'm letting those guys inside my house. I need a lot more trust, and I dont want new guys every time. I want a reliable guy that I can use over and over again.
One of those is well suited to a distributed model with interchangeable parts. Uber provides that distributed network, and that is a moat of kinds. Yes they can be replaced, but you still need a comparable distributed network in place to be competitive. That isn't free.
Their power is in their existing network, and the fact that being a network is a value add to what they provide. For a cleaning service, being in a network isn't a competitive benefit - I'm not looking for the closest cleaner, I want one I really trust.