Entrenchment, local support against invaders/foreigners (despite opposition to the Taliban), further radicalization and funding that occurs during a conflict by proxy parties, is why the US is still there - the Taliban were never in a position to be asking for anything.

EDIT: I'm not defending the US and any coalition troops staying there. I'm interpreting the current situation. Best thing we can do at this point (and 10 years ago) is to cut our losses and GTFO.