Originally Posted by Matt 26z

The actual use itself probably doesn't cause them to break into the cars unless they are under the influence of a mind altering drug that suppresses their self control.

The purchasing of the drugs is often not a victimless crime. That part is likely the motive for breaking into the cars. This is why successful people always get a slap on the wrist for drug charges. It is recognized that there is no victim when they buy or use the drugs.