Why does new york city clean the streets so often? i live in manhattan and they clean 4 times a week?:
It is a number of people living in a small area of Manhattan.  Most other cities that are more spread out will clean the streets less frequently.

In Phoenix, Arizona, they pick up garbage once a week and sweep only once a week.  We are more spread out than Manhattan.

If NYC did not clean as often as it does, there would be a lot of garbage all over the street.