How come “rockstars” hardly ever get arrested for drug-abuse?

I don’t know if I have enough information to say that this is valid…but it seems that a lot of “rockstars” talk openly about like, shooting up or doing cocaine, or weed (do cops even give a fuck about weed anymore?). How come they don’t get busted? Do they have to have it in posession to be arrested?
So they just post bail?
Well like, if they talk about doing drugs, can’t the cops be like “oh, that’s suspicious behavior” and put them through a drug test?