Actually, they kind of are. I mean, if you have a gun and use it to shoot cans in your backyard, or that you take drugs and stay home, or go out but don't drive, don't attract attention on you, don't cause any problem, are you even going to be arrested? You have no idea how busy the police is with actual criminals.
I'm not saying we shouldn't do illegal things that don't harm others, I'm saying we should catch criminals who actually do harm.