A moon base wasn't built because it is already hard enough to build a space station.
Why should you go to Alaska to do some experiments when you can do them somewhere near home?
Furthermore most experiments require not only low gravity but very low gravity to work. What most people tend to forget is that the moon does have a gravity field even if the accelaration is only one sixth that of earth.
The russians had a very neat moon programme but dicontinued manned "deep"
space exploration in favour of building space stations in orbit.
If the US hadn't really landed on the moon the russians would have known and would never have stopped their own programme.