why are there almost no airplane movements during the night at the biggest airports, like atlanta or boston?

Noise.

A lot of airports at major cities close down to most air traffic after a certain time, to keep down the noise in the surrounding neighborhoods. Incoming international flights are still able to land, since they're been flying for a lot of hours. But mostly, it's to keep down the noise.

Because people need to sleep

I do not know where you live, but, I hear them coming in all the time.

So as not to disturb sleeping americans.

Visibility is an issue. It's hard to see the runway clearly, even though it's lined with lights.

Plus, there may be some noise restrictions for the city.

good q probably noise like other guy said maybe also saving money not hiring full third shift to run airports plus many people so not want to take off land in middle of night

How bout a big like Phx AZ. They did slow down at Thanksgiving Day,But never stop

Because both of those airports mainly have commercial activity. No one wants to take a flight that leaves at 2 am. All the internationals are airborne and the transcontinentals are parked for the night, unless you are severely delayed. If you go to Memphis, that place is a Northwest Airlines hub during the day, and a cargo hub at night. Indianapolis is another example. Cargo aircraft operate at night because there are far fewer delays for them, plus throwing them in during the day would make everything else slower.