Uuuuuummmmm, I think you have that backward. Roads were not built for cars. Before yon auto-mobile, there were was a great velocipede movement in all developed nations. These "cyclists" as they came to be known, hated riding their wheeled contraptions through the rough and rutted dirt roads of the time. They (groups like the League of American Wheelmen and the Good Roads Society) pushed, influenced, petitioned and in some instances outright paid to have streets smoothed out so that they could have a comfortable, pleasant ride from point A to point B. They even went so far as to lobby for a national road system in the US, instead of having all roadways paid for by states and municipalities. It paved the way (ugh, lame pun) for and basically morphed into the Federal Highways Administration. This of course would later influence the creation of our current interstate highway system.
The fact that we have modern roads to drive on at all is owed a gigantic debt of gratitude to 19th century cycling enthusiasts and manufacturers.
Basically, bicyclists were lobbying for better roads for a good 20 or 30 years before those young whippersnappers, the automobilists (automobiles, of course themselves being an extension of bicycle manufacturing technology in many cases) began lobbying for the same thing. Oh, and many of the 19th century, road improving cyclists ideals centered on building better roads for everyone to share.
tl;dr bikes made good roads first, not automobiles