The principle is road safety, not creating a city the Stepford Wives would feel good in.
So, leaves and snow are cleared up when they make the roads and pavements unsafe. (It's your duty to make sure that the pavement in front of your house is safe)
It means that you can still see quite a bit of snow and leaves in places where it's not harmful.
Trash is another issue obviously. But natural things shouldn't be cleaned up at all cost.
Wow, those girls must have been really something for you to get so worked up. I don't know what you mean by "all cost" but I do think the leaves should be gathered in the city. If you don't then what? They just stay there and decay. It's fine for a forest but it's not something I want to look at every day. Now snow is another matter, that is pretty to look at
And way harder to gather.
Way to generalize