The problem is that most of the shops/kiosks in the station are either a) convenience stores b)selling food and/or c) selling tourist items,and besides who would want to travel to X station to get a cinnabon unless the person is travelling there and wants it
That's the way it is now, but why does it have to stay that way? And you wouldn't have to build one at every station, but you know that in the AM rush hour, the busiest stations for exiting/transferring are Bloor-Yonge, St. George, King, Queen, Dundas, Osgoode, and St. Andrew. Set up shops at these stations that cater to the morning rush-hour crowd (coffee shops, etc), and then have the advertising geared towards these stations. In the PM rush hour, the biggest stations for existing are Kipling, Islington, Downsview, Finch, Kennedy, Don Mills, and STC. Have shops that cater to that crowd (ready-to-go dinners, etc), and have the advertising reflect that.
Most people would say that this would be an unwanted increase in advertising, and that it would be a nuisance. My view on it is: I'd much rather be bombarded by advertising that might actually be useful to me, than advertising I don't really care about (Viagra, Diet Pills, etc). Because let's face it, we're going to get bombarded either way.