Why don’t they do construction at night?

Depends on where the construction occurs.

In residential areas there are curfews on when construction can take place. In areas were you get less usage and construction noise won’t bother anyone it tends to be more acceptable.

Large industrial sites may operate at night due to isolation.

Freeways can because they are designed to direct sound away from neighboring areas.

Commercial sites are a mixed bag and rely on local directions.