Streets always wet in movies and television?

It is more beautiful visually, especially for scenes at night with the reflexion of the street lights, especially if you're in Las Vegas...

Furthermore, I think it may also be in case of rain, they can still shoot the movie. Let's say there is a sudden shower and then it stops. The movie crew would not have to wait for the streets to dry before they start filming again because rain or not, it is always wet. So they would be less dependent on the weather.

I think perhaps another reason..this is totally a guess...is depending on what happens in a scene and how many times it has been filmed...things ,may have to be washed down to reset the scene. Say if there is bleeding etc. Like I said ...total guess.

when i was watching the movie the warriors and i went to see the additional features the director said that it made more light reflect so the rain in the movie actually helped.

It make it look prettier...when its wet it looks clean and the lights reflect of it for a better visual effect