Is this just tradition? Surely a computer system can see/hear, maybe using night-vision (lidar? radar?), way better than guards can. Then lights can activate and guards can shoot at anyone unwanted who crossed the perimeter .. surely enough incentive?

I think that being well lit will help to deter intruders.

How? Won't getting shot my soldiers be a deterrent?

How will they know if there are soldiers if they aren't lit?