Just for a different viewpoint, I travel a lot for business and rent a lot of cars. The last thing I want to do on vacation is drive. If I have to worry about a rental car, the entire process is WAY too reminiscent of work for me. The busses and other transportation help me relax and not think about work but enjoy it as a vacation.
Would it be quicker for me to have a car and drive places? Absolutely. Would that make it a better vacation for my family and I? Not a chance in the world.