As a matter of fact, they do. The hard stuff would be concentrated caffeine in pill or injectable form. That's what you'd see if caffiene were illegal, and you'd probably be calling it a hard drug and mocking everyone who didn't think it was that bad. If Coke could still contain the substance for which it is named, crack wouldn't exist.
And, of course, there's the example of alcohol. Yes, such things as Everclear or, going down the scale a little, vodka exist. But the drinking of beer far exceeds them.
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.