IMHO, the logic is that catching people in the act (of burglary, robbery, etc) is difficult, and convicting them if they're not caught red handed can be difficu

IMHO, the logic is that catching people in the act (of burglary, robbery, etc) is difficult, and convicting them if they're not caught red handed can be difficult. Catching and convicting people for drug possession is relatively easy. Since we think certain people are up to no good anyway, drug laws let us put them away, without actually having to prove the bad things they've probably done. It's essentially an end run around "proof beyond a reasonable doubt." Laws criminalizing concealed weapons follow a similar logic.