Usually not one agency for all of them. Some are managed by federal agencies. Some are managed by state agencies. Others are managed by the rolling authorities. Others are managed by the city. And even others are then managed by the counties.

All those roads are practically open 24/7.

Meanwhile, for public transit there's just one real agency around me and it doesn't even go everywhere I might want to go. The lines operate at whatever schedule that agency wants to operate them at. Those lines stop at like 2AM so I better be home before that or it's potentially a long walk home.

The government who built the roads without any means of non-car transportation makes you just as reliant on them -- AND the car companies. I'd rather be reliant on collective benefit rather than a corporation who doesn't care if my car is broken down or I'm old and can't drive or I'm physically incapable of driving. All they want is my money. With public/non-car transportation people have the actual freedom. Reliance on corporations is the opposite.

Roads are less complicated and "break down" much less often than buses. They are inherently "better maintained."

The number and type of people who complain when roads are bad means the government pays more attention to that than buses.