All I ever find is nailed and screws.

I pick them up anytime I see one, mostly out of self preservation because I drive my car on the same roads I ride on.

But it does leave me wondering...how are all these nails and drywall screws in the road ALL THE TIME?!

I understand bolts that might fall off or cars. But cars don't have nails or dry wall screws anywhere in them. So where are all these tire killed coming from? Who is riding around with loose nails and screws on the roof that fall into the road? And how come these same people never ride around with loose gold coins and such that I could find instead?