[jwr]

The reason why US bus ridership is so low is because buses are terrible. They are dirty, loud, inconvenient to get onto, often badly designed inside (too many seats, too little space), with unsavory individuals making you feel unsafe. In summer they aren't air conditioned, they seem to be refrigerated, you literally need a coat to stay warm. The fact that they are also slow is just icing on the cake.

In addition to that, the US has a stigma: "only poor people ride buses".

Get on a bus in Europe to see the difference.