Well, Tan, I've never actually been adviced to keep cats in at night per se. I once had this discussion with the rehoming officer at Battersea and they seemed pretty happy that I allow my cats free access day or night. Although obviously we like to know where they are...
I think the common belief that cats should be kept in at night, stems from a backlash against the old superstition that cats must be
forced to go out at night. That's something I could never tolerate and I can see that approach is wrong.
Some cats are quite happy to remain indoors, while others eager to hunt and sniff around would climb the walls if you tried to keep them in. As for road accidents, well, traffic is less at night therefore speeds are greater and cats can travel further without the hinderance of coming up against people and dogs... Fortunately, I've always lived in areas where my cats don't need to cross roads to get to hunting grounds.
Er... I'm not helping your quest much, am I?