Well, part of the problem here is that having sensors get too good, or space too well monitored, breaks traveller canon and (more importantly) the "feel" of the game. Covert operations need to be able to hide in dark corners. Lost wrecks need to stay lost until the player characters find them. If the universe gets too brightly lit, so to speak, it no longer feels like the Third Imperium we all know and love (to tinker with). A game with sensors and surveillance on that scale might well be fun and interesting, but it would tend to feel more like Star Trek or Banks' Culture than like Traveller.