Plus, many rich people smoke crack, because it gives them more of a high than regular coke. People just want the most, no matter what. The legal status has nothing to do with it.
There are also caffeinated mints. All the stuff is less than it would be if it were illegal, because of the basic economics of the situation, and not everyone who drinks caffeine winds up popping the pills. Some people want drugs in a hard form, most don't. There can be small shifts, and the market shifts with demand, but there's nothing to support the idea that in all cases people go for the hardest form they can get. The historical experience with alcohol is enough to prove that.