I think we all know how to effectively counter a stealth ship. But there can be times when a lock on isn't possible if you lack the emissive rounds, and when you're up against a very quick Viper, Eagle or DBS with dark paints it can blend very well into the backdrop. Nightvision eradicates this, which is the sole highlight to my thread here. So it really does stomp a foot down on any silent runners that little bit further.
Some say you won't use night vision during combat but in the black of space, it only lights up the ship, so it could be mighty effective.
“Quick” implies that the ship is moving, which means it’s emitting a lit up exhaust trail, thus eliminating stealth anyway. You might as well hold up a big sign that says “shoot here!”.
As for leaving night vision on in all combat, that’s a bit like leaving your high beams on in all weather. Not necessary. Plus, one of the big appeals of this game is the visual beauty, which NV heavily detracts from.
If you’re leaving it on at all times for visual efficiency, well, I pity the sort of person who is obsessed with efficiency to that degree. Most folks aren’t like that, thankfully.