I don't get it

I was wandering around Berkeley today, after having a cup of coffee at a nearby cafe and spending some quality time with me, myself and a book, when I came across a rather perplexing sign. It read:

Drug-free zone

So, what? Other parts of Berkeley are drug-filled zones? It's cool to shoot up in MY neighborhood, but not on THIS street? Granted, it WAS posted on Telegraph avenue, home to cheap eats, vintage clothing shops, cd stores, and a disproportionate number of Berkeley's homeless/self-talkers/ranters/beggars.

But it still seemed a bit odd. I mean, why shouldn't ALL areas be "drug-free"? My guess is, the designation means stiffer penalties for offenders caught there. But if you're going to give hard sentences to some, shouldn't you do it to all, regardless of the geographical location of their transgression?

Just a thought.