Many airports (in the US, at least) make much more money from parking fees than everything else. On top of that, at least some operate their retail in a royalties model too (ie 20% of all sales goes to the airport, before any costs).
Thus, there is very little incentive to keep you in the airport less, and multiple incentives to keep you there longer.
Thus, there is very little incentive to keep you in the airport less, and multiple incentives to keep you there longer.