Space tidiness.

"I need you to get aaaaall the way off my back about the garbage compactor" - Screenwriter Guy

wink, you can still track lesser number of objects easier tho

The human mind has a hard time conceptualizing the ostensibly infinite. In short, mind clutter.

Small airlock doors, obviously.

Ejecting garbage into space during battles and fleet maneuvers could damage their own ships, so they had to be prepared to store it for hours or days. But trash is bulky, so they compacted it. Also, maybe compaction was followed by incineration or some other processes to destroy any potentially cl...