It's rude to not consider someone else when living together.
Rob needs to get something from downstairs in the middle of the night, and he lives with a roommate.
Rob wants to get the item and get back to his room.
Rob makes sure to move quietly while retrieving the item as to not disturb his roommate given it is the middle of the night.
Rob moves quickly through the home with loud footsteps as he goes to retrieve the item from downstairs.
Rob's roommate sleeps through the night unaware of Rob's movements because they are quiet.
Rob's loud footsteps going up and down the stairs in the middle of the night wake his roommate who doesn't appreciate the broken sleep.