I could do a lot more damage to the fixed wing aircraft given half an hour with a sledge hammer. Assuming that avionics etc have been removed, it's hard to understand why the airframes have been left relatively intact - unlike the helicopters.
However unlikely, it reminds me a bit of Albert Speer's decision to leave German infrastructure intact pending likely post-war reconstruction (thereby countering Hitler's scorched earth order). Maybe the Talibs are expected to turn them into crop sprayers - which might help them grow more Poppy as part of Afghanistan's "economic reconstruction".