I think that this is purely down to money. English counties don't have the funds available to be able to pay Indian players to play for them.
I mean can you really picture MS Dhoni playing on a cold Aprils day for my side Kent, infront of a man and his dog for peanuts??
I never wants Dhoni to play that way.I asked the young indian seamers to play county.I don"t think that seamers like Praveen Kumar,Yadav,Shami Ahmed,Dinda and even Nehar is that costly for county teams to afford.most of these seamers are looking for a comeback and the Indian conditions are mostly against seamers.So they should try play county cricket for a comeback.