I have contributed to many threads on here since recently joining and find the majority pleasant and enlightening reading, sometimes sad, sometimes happy. However, there is always one that has to be rude or spoil the 'atmosphere' by taking things too literally or to an extreme, seemingly deliberately misunderstanding the OP. Not too hard to find who the prize goes to today.
That said, and back to the original post: I find it hard to understand people who have the best, most powerful, most expensive, biggest etc. not out of need but just because they can. Even if I had the money I would not waste it, would sooner help others. But I have realised in this life that even though we are called upon to use less energy, save the environment and so on it is only the poorer members of society who do this (there may be exceptions). I do my utmost to save energy by running a small VW Up! It is roomy and fuel efficient and only costs £20 road tax. I fill a kettle with only the water I need, switch of lights, TV etc when not in use, put an extra woolly on rather than up the temperature, I could go on. But my point is that I am pretty sure rich folk do not do these things in order to save a few bob, why would they when an energy bill is insignificant to their bank balance? So, to answer your query, I guess many folk buy bigger, gas guzzling vehicles just because they can, not out of need. They either have the money to do so or don't care about the environment, or both. But please, do not misunderstand this post.....there are many who probably do need the bigger cars for whatever reason.