A lot of reasons or more correctly a lot of interests are effected:
1. Much of the Army hierarchy are determined the US should not leave without something that looks like victory.
2.. The trans-nationalists see it as a permanent source of pork for K Street.
3. The CIA finds the endless war good for career progress and for lots of untraceable cash from the drug trade.
So you see it is the people that matter that want our presence to be permanent. Those who are killed or maimed are mostly just white, cis-gender, hetero-normative males whose toxic masculinity makes their deaths and wounding a positive outcome.
"How dreadful are the curses which Mohammedanism lays on its votaries! Besides the fanatical frenzy, which is as dangerous in a man as hydrophobia in a dog, there is this fearful fatalistic apathy. The effects are apparent in many countries. Improvident habits, slovenly systems of agriculture, sluggish methods of commerce, and insecurity of property exist wherever the followers of the Prophet rule or live. A degraded sensualism deprives this life of its grace and refinement; the next of its dignity and sanctity. The fact that in Mohammedan law every woman must belong to some man as his absolute property, either as a child, a wife, or a concubine, must delay the final extinction of slavery until the faith of Islam has ceased to be a great power among men.
Individual Moslems may show splendid qualities thousands have become brave and loyal soldiers of the queen: all know how to die: but the influence of the religion paralyses the social development of those who follow it. No stronger retrograde force exists in the world. Far from being moribund, Mohammedanism is a militant and proselytizing faith. It has already spread throughout Central Africa, raising fearless warriors at every step; were it not that Christianity is sheltered in the strong arms of science – the science against which it had vainly struggled – the civilization of modern Europe might fall, as fell the civilization of ancient Rome."
-Winston Churchill, The River War
In retrospect, maybe we should’ve convinced the USSR to stay in Trashkanistan. “Can we get you anything, comrades? A little vodka? Some fuel for your helicopters. Oh, wait. Already asked you if you wanted some vodka.”