Its because we are all smart!!!
Beats going out spending 30k on a 1.2diesel "because the road tax is only 156euro" then selling it 3 years later for 15k thinking you have saved a fortune on tax.... :huh:
I think its also down to boredom, most modern cars are a snore fest to drive so having our own "stamp" on things on maybe something that's 10-15 years old or older make us feel better.
I think being into cars is only the start of it, it goes further then. Some are into engines and mechanics, others into cleaning and detailing, others into modifying the car all round.
I love all cars, but BMW more then most but do appreciate other stuff like Jap cars that make 200BHP from a 1600cc engine, I think people that get stuck into the "I only like BMW" or "I only like Honda" are not into cars IMO....
Probably gone a little off topic