Cars are terrible at scaling. The core problem is roads take a lot of surface area so adding traffic lanes reduces density which forces longer commutes. Add to that you need parking at both ends which reduces density further. http://streets.mn/wp-content/uploads/2014/09/car-vs-bike-vs-...

They are also worse for the environment and kill lot's of people.

PS: Cars also have huge direct and indirect subsides, consider who pays for your parking space while at work? Hypothetically in a major city ~2 * 100$ parking spaces + ~100$ insurance = ~300$ a month or 15$ per workday day even if your car, gas, and roads where free.