The cause of too many vehicles

These past view days, i have been asking some of my housemate about what do they know about the cause of too many vehicles, and from the answers i conclude that generally to them, the cause of too many vehicles in the road all over the world are because the number of private vehicles increase as the population increased, the import of vehicles increase year to year, capable people increased every year depends on the economic situation, public transportation not feasible, and people easy to get driving license except in Singapore.