They are not supposed to, but they do sometimes cheat at airports. I had it happen to me a lot at IAD when I lived in Reston. The scam was that the driver would call you, ask your destination, and if it wasn't D.C. (lucrative) they would cancel your reservation. Since then I refuse calls from Uber drivers when I am at a US airport.

Uber drivers tend to prefer to take long 50 mile trips. Mo money.