I second this. I rent cars between 5 and 20 weekends a year, and have been doing this for about 6 years. It works out fine. The car is always in perfect condition, and it is not that expensive. It is true though that some trips that do not reach the importance threshold don't happen.

Also, taxis work well here in my hometown. About £8 will get me to the other side of the city, and a weekend hire costs about £50. I found owning a car, all-in, cost about £200/month (adding up tax, insurance, repair bills, etc) so it's cost-efficient to hire a vehicle when I need it.

Before we had our own business (necessitating a vehicle) we spent a couple of years without a car - for 2 people it was always cheaper (sometimes quite a lot) to hire a car than it was to take the train. Such a shame as I generally love travelling by train.