Well, so much for the night yielding answers...
Possible reasons for no kill:
This is a game of stock only and we're all town
(Seems super unlikely as the rules in OP specifically spell out that there is mafia and town wins when they are gone, I know the rules are generic and pasted from somewhere but a mafia game without mafia I would expect that kind of stuff to be removed from the rules)
Town got lucky or are better than I can imagine
(Someone got blocked and somehow the kill didn't happen)
Mafia has to either challenge or kill, can't do both
(Still if that is the case, they would be better off just killing someone I would imagine)
Mafia somehow opted not to kill
(Is there any conceivable strategy where this would make sense? In my mind Night 1 kills would be the safest one for scum?)
I am overlooking something? For people who play this game a lot, does it happen frequently that there are no kills on Night 1 and if so, what is typically the explanation?