The buses in SLC are clean and friendly. The only buses I have experienced hostility with are Greyhound, and that hostility came exclusively from the workers. What's the difference between my city and yours? Budget? Population? Probably a mix of both.

It's incredibly unlikely that there is one coherent cause for low or high ridership. All we can do is improve the utility of the service. That means improving comfort (keeping it clean), reliability (running on time with minimal detours), throughput (carrying enough people), speed (minimizing the number of stops on the route), latency (minimizing the wait until the next bus), availability (more stops that service potential destinations), and coherence (more routes that take you directly from A to B, minimizing transfers).

Personally, I feel most undeserved by latency: the routes that are convenient to me run every 30min, and the routes that run most often run every 15min. I would ride the bus way more often if routes ran every 10min. I would ride them all the time if they ran more often than that. This seems like a pretty obvious opportunity that will never happen so long as prospective budget is determined by current ridership.