Expenses and diminishing returns. NASA is not America’s “space agency.” They are, by letter, a temporary government agency whose goal is to commercialize and create a space industry. This is. We only built the shuttle to put the NSA’s spy satellites into orbit and, critically, to retrieve them.
You can say we were there because we left shit there. You can imagine these things as civilian if you trust the observatories from where they are made. And we use the various retroreflectors left on the Moon constantly for experiments and other experiments.
Otherwise, the moon sucks. The powder is fully dehydrated and acts like sandpaper against all mechanical joints. It has moonquakes. The day/night cycle lasts a lunar month, so temperatures are extreme and power generation is a big problem. And you have to keep your life support systems running in this environment all the time, there is no natural shelter available.
Until we can figure out how to mine it or build a dome over it, there’s almost no reason to be there.