I don’t know more than they do but here’s a really good guess…
Maybe it’s because they are in negotiations and showing their ability to infiltrate even NATO ranks is a major card in their hand? The Karzhai Puppet Government and their NATO Overlords “liberators” say, predictably, that the document published on the Taliban’s Web Site detailing the plans for security at the loya jinga (congress, parliament) meeting is “forged”. Why WOULD they show one card out of many in their hand, one that says “Ha ha, we’ve got our people everywhere, including the NATO command structure”? Yes, why would they demonstrate their strength in a subtle way like that rather than acting like the crazed barbarians that NATO propaganda paints them to be?
Oh, and in case the point was missed… on a Web Site the Taliban maintains
But we’re supposed to think of them as subhuman inferior savages who are incapable of civil behavior. Suddenly it’s not very easy to look down on them.
Like the “Civilized” NATO StormTrooper Thugs who shoot babies and launch Terror-drones against people without even knowing exactly who they’ll kill. Real Ubermenschen, they are.
Part of the NATO propaganda is the Karzhai Terror Government is superior to the Taliban because he was educated abroad, meaning, “Taught how to behave like a White Person”. Of course, nothing racist about that.

Or the idea that the White NATO Liberato Overlord Massa Boss-Mans have to stay there because even their puppet Karzhai is “too savage”.
Perhaps the British puppet Raj was really to protect Afghanistan against the Turks, as claimed. Or, in an alternate and entirely believable scenario, the Afghans had stopped the Turks, and their social and ethnic predecessors the Byzantine Empire. And the Romans. Also the Persians, and even Alexander, conqueror of just anybody you could think of… wouldn’t even try to conquer them. Toss in Peter the Great of Russia. But of course even with all the attempts to break in and rob the country blind, and then come back later for the white cane and seeing-eye dog, they were “isolated” throughout their entire non-centralized society and absolutely NOBODY could have possibly learned how to deal with the “Civilized” conquerors on equal terms.
And, imagine that, they defeated all the previous empires while the British were still living in mud huts.