Primarily because they aren't doing their research (cars aren't their thing), so they have the dealer or mechanic do maintenance and/or get terrified when the odometer is close to "out of warranty" so they have to get into a new ride. These are the guys who are like, "I just spent $1200 on brakes and rotors! I love my Toyota!"
Car guys can be happy on budgets as low as $1k to as high as $1,000,000.
It's a hobby. It's a pastime. It's a community and culture. It's not a mutual fund, the whole idea I have to justify my fleet costs as some sort of asset is absurd. My cars are not part of my retirement planning, nor should they be.