Why do people drive SUVs?

I understand that its nice to have a big car but it is really worth the extra cost both to running the car and to the environment? There are loads of fuel efficient people carriers around for people who have families of 5+, my father has one and they are very comfortable and spacious. why bother with an SUV? surely they are much more expensive, difficult to park and now are they banned from some city centres in the US? I just want to know what makes people still buy them? Is it down to liking the look and feeling safe in a car whilst putting other road users and pedestrians at greater risk?
I understand when people need 4 wheel drives eg. when they own lots of land and need to access points off road, but surely the majority of people in the US do not take their SUVs off road? please correct me if I am wrong here.

Also would you still buy one if you knew that if all the sports utility vehicles in the US were replaced by cars with fuel efficiency equal to the European average, the emissions savings would be sufficient to supply electricity to an extra 1.6 billion people (that is more than the population of China)?