Why does the government need to place restrictions on where people build? If I build a house without flood insurance and it gets washed away, it's my loss - why

Why does the government need to place restrictions on where people build? If I build a house without flood insurance and it gets washed away, it's my loss - why does the government care? Because the cost ends up showing up in other ways. Maybe it costs more due to social safety nets needing to take care of those who lose their houses without the means to replace them. Maybe it means an increase in crime as those who lost homes/stuff get desperate if they can't recover from such a loss financially.