Why do so many airlines want that you stay at least a night from Saturday to Sunday at your destination.......

Question

..... to give you the best prices (elsewhere they are more than triple as high or more than that)?!

Answer 1

Mainly to get the top dollar out of business travelers.  Saturday nights are the least common nights for business travelers to be away from home.  A lot of business travel needs to happen regardless of price... so that's the easiest way to differentiate between most business and leisure travelers.

Answer 2

I agree with the first answer but that is not true for Southwest.  They were designed for the buisness traveller who commutes daily with high frequency flights available.