'Throwing' your trash out on the street every week is a solution to the trash problem which probably accounts for a lot of smell. I bet if they stopped doing that then it would improve a lot.
In NYC, they can't stop doing that. I read an article about this very thing not too long ago. The problem is that NYC (Manhattan actually) doesn't have alleys, like other American cities such as Chicago. So there's no place to put dumpsters or trash for trash crews to pick up, except right out on the curb in front.
More frequent pickups could alleviate the problem though.
More frequent pickups could alleviate the problem though.