It is, but there are still many neighborhoods where members are concentrated...
Give me the numbers. What do we have? A few thousand active members (idk what the threshold is to qualify as “active” and I have no idea how to quantify whatever your definition is.
How many member are interested? 5%? That’s a few dozen geographically dispersed members, most of whom are interested but don’t own a car. Owning and maintaining a car is costly and a hassle, with the additional hassle of shuttling a car back and forth with your sharing partner. Gotta figure out the logistics and economics of it.
Then there’s scheduling, who gets the car when. My guess is you’ll oftentimes have overlap between high and low peak demand, both sharing-partners really want the car on chol Hamoed but don’t have any use for it on a three-day YomTov.
Add a third sharing partner and you get better economics, but the logistics and trust becomes more complicated.
I see it as too complicated to work on a grand scale, but two members who are really committed to the idea and are willing to work out all the kinks to make it work might pan out.