This depends on a country, I've seen some where it's municipal bus, that is overcrowded, and mini-bus is a more "premium" service. But anyway, do you think you should force them to pay twice the price by removing the overcrowding? It's just a revealed preference, like with airplanes, people prefer price to comfort. Modern startup in this area can experiment with a different price for standing/sitting.

If this jitneys are really worse, there is no need to forbid them, municipal buses will outcompete jitneys.