It is important to take care of your car to ensure it lasts as long as possible and maintains as much efficiency as it can. This may involve taking it to the garage whenever a new potential fault appears and checking the basics of lights, oil levels and other functions frequently yourself.
It is also important to maintain less obvious things too. A dirty car may not look good physically, but it can also damage the paintwork if there are chemicals in the muck, for example. This may be a problem for people who live or work near industrial sites or other similar places. Once the paintwork is damaged, it can gradually lead to rust and other problems.
Maintaining the inside of car can also be worthwhile. Some people find it easy to pop rubbish on the floor, but then as time passes forget to pick it up and soon enough the car is covered in little bits and pieces that do not need to be there. While it is not an actual issue in many ways, psychologically the mess can cause people to think differently about their vehicle and take less care of it in the more important ways too.