The nicotine gets everywhere. Someone on Autopia posted a few months back about cleaning a smoked in car. He said the nicotine was everywhere like a sticky film. It even seeped through the carpet and when he lifted it up the nicotine was on the backside of it. I'm sure if you aren't regularly cleaning the inside of the glass that you have a pretty good film of gunk on all the windows inside, so that could very well be the problem.

i do smoke with all the windows ans sunroof all the way open no matter how cold it is but i will clean my window with some windex degreaser for glass and i wont smoke in the car anymore to see if that helps..

so far that the house, the basement, and now my car.. if i did'nt have a garage it would be a small reason to quit.. its too cold to stand outside just for a smoke.. i dont need to freeze....

It could also be whatever you are spraying in there.

I SPRAY AUTO FEBREEZE AND I SPRAY IT ON THE FLOOR AND HEAD LINER ONLY..

Do you take the car through a lot of automatic car washes? I've noticed after that wax gets on the windshield a few times, I guess it builds a layer and kind of makes things a bit blurry. I wonder if some vinegar and water wouldn't get that layer off. I only go through the touchless automatic if its below 30 degrees in the winter. Any other time I pull it in the bay for a quick spray down or do it at home.

no car washes... i always spray it with th epressure washer first to remove loose dirt and pebbles then i hand wash it for that one of a kind shine....

but yeah i have cleaned my inside windshield with windex degreaser and now its alot better .... i just also noticed alot of little pebble marks on my front windshield.. which means a replacment is due soon..