We've seen this come up a lot recently with Tesla's move to fine drivers who "park" at charging stations. Many see this as actually worsening the problem as people are happier to pay the (relatively small) fine.
Even then, Tesla can very easily just increase the fine (or do something like a steadily increasing fine) to address this concern. They could also charge additional fees to anyone who leaves their car at a supercharger for too long serially (and my guess is that these are the real problem).