I don't think that's necessarily the case - e.g. "Let's share my car and you can help me clean it at the weekend" is a valid sharing arrangement (i.e. share the asset and share the effort to maintain).
Well, we're deep into worthless pedantry here, but I love worthless pedantry.
I would say that despite the casual use of "share" such as in your example, that isn't really "sharing". It's bartering. The use of the car is predicated on getting something in return, so it's an exchange of value.
I would say that despite the casual use of "share" such as in your example, that isn't really "sharing". It's bartering. The use of the car is predicated on getting something in return, so it's an exchange of value.