Videos in Syria are usually from flat and open terrain, NLOS ATGMs aren’t common even with modern militaries.
The TOWs in Syria did come from Iraq, the Kornets came from Iran.
There is also the possibility that the Taliban after fighting the Americans for nearly 2 decades also has pretty good opsec they know that the US tracks phones even when they are out of cellular range and in general they came to believe that pretty much anything with a battery can somehow be tracked by a drone with a SIG/MASINT pod and they are probably not that far off.
Looking at both photographs and some battlefield photos they use plenty of man portable rocket
systems like RPG-29 and 32.
Guided systems are more complex, heavier and usually require a team to operate. Hauling them on foot in the mountains isn’t ideal and their range is limited since these are still WLOS system at that point they offer no real advantage over RPGs and other unguided weapons.
Also keep in mind that the fighters in Afghanistan are far more likely to be illiterate which means they aren’t likely to be using sophisticated weapons that aren’t point and shoot not to mention mobile phones.
Syria had both a much more modern population to recruit from and far more foreign fighters than Afghanistan has now.
Looking at their weapons and tactics since post 9/11 if indeed they aren’t using ATGMs at the same prevalence as say Syria there are far better explanations than they can’t afford them.