Rover's guidelines state that the "nightly" house-sitting rate includes up to 24 hours of care. IMO house sitting is a premium-type service because you are not only caring for an owner's pet but also their home. There would be an expectation that you stay overnight in order to provide that level of care.
However, on Rover, sitters are independent and can provide whatever service they'd like so long as they communicate it to the client and there's agreement. Some house sitters will use the client's home as a base of operation and service other clients for walks, etc. Some will only come to the house in the evening and stay until morning because they have full-time jobs or are students, but they will also check on the pet during the day. Some will include those visits; some will charge on an a la carte basis.
As I have written, I do believe true house sitting commands a higher fee due to the greater responsibilities and the inconvenience of having to uproot yourself. However, at $100/night, a client would not only expect you to stay overnight but also to provide care throughout the day. If you are not getting house sitting jobs, then the market has spoken.