Oh, it's not human nature so much as complexity. Carpooling is most popular for regular commutes at set times, for exactly this reason.
When I decide to visit the hardware store on Saturday, there is probably someone I have never met that I could carpool with. But how do I contact them and arrange a carpool in minutes? If I have to post a listing a week in advance, it just isn't worth it.
When I decide to visit the hardware store on Saturday, there is probably someone I have never met that I could carpool with. But how do I contact them and arrange a carpool in minutes? If I have to post a listing a week in advance, it just isn't worth it.