We're done. Satellite valves are shut. Now bleed the hose pressure off into our tanks. We want a clean disconnect.
Why? So we don't pollute our pristine vacuum?
Exactly. There's no breeze up here, nothing to move debris away. If you're not careful, you end up with a cloud of muck around your satellite.
In space docks, where there's painting, lubricants, welding and grinding, it gets to be a real problem. In some docks, your time isn't limited by oxygen but by how long your suit visor remains clean enough to see out of.