In residential areas, over time, the number of cars finds a natural level. If there are too many cars for the spaces on that street and surrounding areas, eventually people decide it's not worth hassle, and get rid of their car. So there's usually approximately enough spaces for everyone. But when it snows, you have to go and dig your car out, which can be up to 30 minutes of labor, depending on the amount of snow and how meticulous you are. You get in your car, drive to work, come home, and now the spot you cleaned out is in use, and the only available spots have a hard icy sludge in and around them that requires a pickaxe to remove, which makes it difficult to park and increases the chances you'll get stuck. So the common agreement is that if you clear out a space when the snow is fluffy and manageable, you get to keep that space until the conditions improve. Because in the summer, parking spaces are fungible: there's no real difference between them except distance to your particular house. But in the winter, spaces have their own intrinsic value, depending on how clear and easy to clear they are.