Demand is absolutely elastic (to a certain point) on a number of dimensions: price, time, comfort, hassle. There's an upper limit. The trip from A to B usually has some negative utility relative to being at B but the closer to zero you can make it, the more likely you are to make the trip.

Personally, I just don't have many situations where I would make a trip but my available alternatives are just a bit too costly/inconvenient--while Uber wouldn't be. But I understand they exist.