Others have given great answers. I'll add just a little more. There's a concept of cislunar space, cislunar infrastructure and a cislunar economy - cislunar just means the space between the Earth and the Moon. LG is one component piece of a future cislunar infrastructure that facilitates lunar satellites, transport to and from the surface, rapid escape in the case of catastrophe on the surface, and it's all local to the Moon. It's, at least on paper, an efficient way to do Moon missions and the starting point for mining ice to turn into rocket fuel to send us on along to Mars. Long term, LG replaces some of the existing Earth-based space infrastructure.

There is also a geopolitical aspect to this, as China is firmly set on going to the Moon and building stuff there. So if China sets up a Moon telescope peering back at Earth or if China starts mining helium-3 and corners the market, or whatever, the competing powers want to be able to do the same thing. And LG and cislunar infrastructure are important parts of showing Moon capabilities and answering China's accomplishments as they occur.