Even AirBnB isn't sharing though, in the traditional sense of the word. This should be obvious when you compare it to CouchSurfing, which is genuinely about sharing.

I would argue that the way it's traditionally understood, sharing is something that happens between equals, or people who have an intention of becoming equals. "Let me share some advice with you" is fundamentally about a relationship between equals or possibly a relationship between people who are not exactly equals in some aspect, but either feel like they belong to some common in-group or like they will be equals eventually.

From this perspective, it's obvious that CouchSurfing is sharing while AirBnB isn't: on AirBnB, the expectation is that there is a split between the seller and the buyer; on CouchSurfing, there is a shared identity of "travelers" and an expectation of reciprocity.

Let me also point out that by your own definition of how you use the word sharing, it's not so clear why you wouldn't call Uber a sharing service. After all, somebody might decide that their car is an underused asset which should be "shared". (Hold on, you say, those people are also selling their labor? Well, so do AirBnB hosts when they clean the room after you stayed in it...).

tl;dr: Your conclusions don't actually follow from your implied definition of sharing, and your definition of sharing doesn't match the general feeling that the word evokes.