I know how annoying this can be, especially in some countries this behaviour is often directly associated with criminality. Here in Switzerland dealers are often (not always) just that, they make enough to not bother with anything else. They don't look like "dirty" junkies, they don't bother stealing from tourists, they basically don't look for any extra attention when the business is rolling anyway.

Survival bias: the police would come down on them on hard if they were scene as disrupting social order. They have to not look dirty to survive, Swiss police are no joke.

When I was in Amsterdam people were offering hard drugs on the street but "no, thank you" was perfectly sufficient response