Renting cars means you can avoid a lot of car ownership-related work & admin. This includes the paperwork such as road tax, insurance, breakdown cover, parking permits, MOT etc as well as the direct admin such as filling it with petrol, finding a parking space, washing & cleaning the car, putting air in tyres etc.
Renting a car from commercial companies can also involve a lot of hassle especially if it's only for a short journey - you have to go to their inconvenient location, queue up, get upsold lots of things, be asked a million questions, get shown the car, sign lots of forms... the list goes on. Sharing a neighbours car is convenient, quick, and generally a very pleasant experience - it's nice to meet local people.
If you're interested in more tips on living car-free, see Giving up your car