Ya in some cases Airbnb can be like Couchsurfing if the host is there in the same apartment/house and actually more of a host/local guide, and I think some Couchsurfing hosts may have transitioned to Airbnb, but there's definitely a difference in what the "default" expectation is
We've been hosting both AirBnB and Couchers/CouchSurfing.
AirBnB has the vibe that you as the host are a provider of a service, which will be rated by the "customer". Couchsurfing is just some people hanging out.