Just like for schools, healthcare, roadwork and every other _public_ systems/infrastructures in most European countries.

Everyone is better off that way, I pay for roads and public transport I very seldom use, but other people paid for my education and my medications. At least I won't die because I can't afford insulin or go bankrupt if I have any semi serious disease/accident.

At the end of the day that's exactly how any insurance work, everyone give in all the time and a very small portion of the population gain from it at any point in time.