Shining Bright American cars

Can anyone explain why American drivers must kept cleaning their car
all the
time? Here in California street, looking around almost all the cars in
street,
most are shining bright. American drivers must be addicted driving
clean car. I know that AMericans are addicted to automobile. It seems
to me that driving fresh shining automobile are American addiction
next to eating and sport .I simply can't understand why Americans are
so addicted to fresh shining cars. Why they must kept their car clean
all the time?