It’s nice to be neighborly, even if you don’t actually see your neighbors that often. When you live in an apartment it’s good to meet the people who live around you, or at least to introduce yourself at some point. That can make it easier for you later if you need to ask them to turn their stereo down during the early morning hours. Or perhaps they will ask you to turn yours down instead of calling the police.
There are a lot of easy ways to be neighborly, like waving to people as they pull out of their driveways, or offering to help carry groceries up stairs. It’s always nice to know the people who live next door are happy to see you.
Maintaining good relations with your neighbors can open resources to you that you may not otherwise have. For example, if your toilet gets plugged and you don’t have a plunger, you can go borrow one from the people who live next door.
You don’t have to be best friends with your neighbor, but a little conversation now and then can go a long way.