It means that when I come home and open my garage door, also neighbor's door opens. Not a big deal, you may think, and definitely not my problem. I agree, but could you leave your neighbor's door to the garage, where two thirds if their stuff is boxed, open? in the middle of night when you use your remote to open but shut your own door with different frequency button and neighbor's door stays open.
So in the mornings I open and shut my door, go ring neighbor's doorbell to ask them to close their garage, but nobody is home. Then I open (and wake up my poor little child with cold again) my garage which shuts neighbor's, run back in, close my garage door, check that neighbor's is still shut, get out of the front door ans shut that. And leave for work.
I just hope that new neighbors appreciate my continued action to keep their belongings safe!