Tobbaco, Cannabis, Amsterdam?

Within the next month, the Netherlands will be enforcing a ban of the smoking of tobacco within coffee shops and other catering business'. However, with this ban, cannabis will still be allowed to be smoked while tobacco will not.

Any idea why this is?
tobacco smoke have been shown to cause disease and death. believe it or not, marijuana smoke have not been shown to cause such things, even thought they've tried to look for it.

plus, the whole raison d'etre, the complete purpose of the coffee shops is that it's the one legal place to buy and sell marijuana, so banning it in that would be silly.
i'm sure you can still smoke tobacco in brown bars, where they vend beer, and you can't smoke marijuana in those.
Because tobacco has more carcinogens and it would interfere with the benefits cannabis produces for cancer victims taking it medicinally.