Running buses more frequently has its own problems. When a bus is running slightly further from the one in front than it should, it has to stop more often for passengers, and those passengers take longer to buy their tickets, which makes the bus run even later. This is a positive feedback loop that is made worse when buses are more frequent. I have certainly seen a set of four buses coming as a convoy on a route that is meant to have them every 12 minutes.

The solution is to either run fewer bigger buses, or to inject a whole load of negative feedback into the system, either by having buses wait for a minute at a few stops until their scheduled departure time (which involves making the route slower) or by real time tracking with radioed instructions to the drivers, like they do on some underground train systems.