I was asked this question:
Why do the derby cars break down so much?

I laughed, and then had to think of the best way to answer this question. This was my answer:

You know that car you drive the family to church on Sundays in.
OK, fast forward about 20 years with that car. It sat behind someones house broke down for the last 5 years because it had a dead battery and they didn't want to spend the money on a new one. So the derby driver bought it for $0-$100 and had to tow it home.
Get the car just barely running putting the least amount of $$$ into it.
Rip every fancy feature the car has out (Interior, seats, windows, lights, everything that makes the car comfortable)
Then, add about 1,000 pounds of steel to re-inforce the doors and build a roll cage. Weld the doors shut, chain the hood and trunk shut, cut some holes in the hood, relocate the gas tank and battery inside the cab next to the drivers seat.
Hop up the motor, cut the exhaust off to make it loud, get a high flow intake filter.
Then find the biggest tires you can get for dirt cheap and will fit on the car.
And finally, drive the car is hard and fast as it will possibly go, while getting a fender collision every 10 seconds.

That is why derby cars break down so much.