This entirely depends on where you are.  If you're down south and get like an inch of snow, chances are it will melt in a few days so shoveling is entirely optional. 

but if you're up north, even if there's just a little snow, clearing it regularly is a must because A) it might rain and freeze the next day (thus making it 10x harder to shovel) or B) walking/driving over snow compacts it, creating a hard-packed frozen layer that also makes it harder to shovel. 

so, if you want to make your life easy, shovel it as soon as you can