Why was there no law enforcement during the daytime for many centuries?

Answer: There was no law enforcement of any kind. In a lot of places, there was no law. I know that in Britain for a long time people visited each other during the day, because it was dangerous to go out in carriages after dark - that's when the robbers would accost the carriages and rob the people inside. Then Sir Robert Peel invented the police - that's why they're called "Bobbies" in England. That was when he was Home Secretary in the 1820s. Later he was the Prime Minister.

Those castles and fortresses in Europe were so people could hide behind the walls. That was their major protection.