So like any business, a network whose sole goal was ridership would focus on those successful products. They would run little or no all-day service to low-density suburbs, because ridership on that product is predictably low. So when transit agencies do run that low-ridership service, as most do, it doesn’t mean they’re failing, as anti-transit conservatives often assume. It just means they have a goal other than ridership.
This is kind of ignoring the fact that while those suburban routes might only carry 5 to 10 people per run, that adds up to a few dozen once they get to the central part of the city and dump all their passengers onto the main bus routes.
I live in a bi-nodal city with a bus system that pulses out from the cores, and three main routes connecting the two main cores and the mall located exactly between them. The routes that pulse outward are, for the most part, under-used by their passengers. But once some of those routes get to a core, they become one of the routes that goes from one core to another, keeping most of their passengers and picking up any passengers from the other routes.
While the bus routes between the cores are actually profitable and busy at all times, they wouldn't be that way if the 6 or 7 feeder routes in each end of the city weren't supplying them with handfuls of people at a time. Lose the suburban routes, and ridership on the mainlines get cut in half, and the whole system becomes less profitable.