Except for the fact that they are not inaccessible to you. Get a bicycle. The only thing that is not, at least in America, are the Interstates and some highways which are mostly funded by gas taxes anyway. The Roman pleb walking on the highway to the market to buy his daily gruel isn't much different than the American driving on I5 to Wal-Mart. And note, the Romans banned vehicles in many cities during the day. The merchant with his ox cart had to come in at night. We have no such restrictions here on commerce, although they have been proposed. Vacationing Roman nobles and wealthy merchants used the public high roads to travel as did the common classes. The difference was the common classes could not readily afford to travel whereas they can now. As such there was a greater public interest in the roads as a means of bringing goods to the people and less public interest in bringing the people to the goods than we have today. That doesn't mean commerce was exclusive or even had a priority. In cities roads often banned vehicles (commercial) traffic during the day so that people could more easily use the public roads for whatever private use they desired without "heavy" commercial traffic clogging up the roads. There's no philosophical difference between public roads now and public roads then. The difference is mobility. Society is more mobile in every way. Instead of 5% of the population traveling rarely, 95% of the population travels frequently. Same holds true for commerce. I seriously doubt the average Roman got his eggs from a hundred miles a way. That's not uncommon now.

If by domain you mean use, well yes it joins a long laundry list of public services that are used by individuals. Libraries, schools, museums, parks, public transportation. Is your point that governments should not spend tax dollars on public transportation? No spending on roads that's for personal use, but more on public transportation because it's for personal use? Err, okay. Logic, unnecessary much? Or did you just not have a point beyond your apparent believe that Roman roads weren't used for personal travel? If making up fallacies about Romans helps you ignore the fact that cyclists in America were an instrumental (in fact for many years the instrumental) driving force behind an expansive public road network go right ahead.

I know this might be a novel concept but society does not revolve around "many of us" (and by many, we're referring to the very small minority that cannot afford a car). The narrow interests of a self-declared "class" do not and will not trump the majority interest. I view buses as you do roads. Gigantic, inaccessible wastes of tax payer dollars. My two feet are generally quicker, so why the hell would I pay for a bus with my tax dollars. Still, despite the fact that buses as used in America are not good for the environment, not economical, and not practical when compared with even inefficient personal automobiles, society apparently feels they are worth funding at levels I don't feel are justified. That doesn't mean I'm making up some hoopla about class warfare or drawing up imaginary "us versus them" lines in the playground and it doesn't mean I'm anti-bus. I'm just anti-buses that don't make sense. I also happen to think roads should be paid for by usage fees and not unrelated taxes on property, sales, or income. Society doesn't agree with me there either. Go figure. Who would have imagined a country of 300+ million wouldn't conform itself to me me me?