So are you tired of people asking you why you do not have a driver license? The good news you are not obligated to explain this to people, and the incessant busy bodies will stop inquiring if you never bring it up.
Living in an urban area means you might even connect with fellow pedestrians as well. Besides, walking and biking are great work outs and save on the gym bill. Pedestrians are green to begin with, and we are greener than people who own smart cars. This is not about being smug, and I have nothing against people who choose to drive, but the truth is when I was younger I felt grilled by people who believed driving was the only way to get around.
If you are tired of being told that you have to get a license and a car, then stop feeling like you have to do this. I think being an introvert made being a pedestrian less of a stretch for me because I have always pretty much done my own thing, and I never really tried to live up to social expectations.