Yup, if you're living close to the T and/or active bus routes you can survive. I have friends who haven't had a car in 20 years. They do use Zipcar on occasion, like if they want to do a Costco run. Uber is also available if on occasion you need to get somewhere not on the public transit routes, though obviously I wouldn't suggest that as a way to get to a regular stop like work or groceries.