As people explore the game, they mention, online, things they have discovered or created. I may want to have a look. By far the easiest way to do so is to jump to the system in question via a portal. Portals can only jump within a galaxy.
No Man’s Sky has 255 galaxies. It’s costly to jump between galaxies. Thus, to view anything found in the game, I need to build at least 255 bases, one per galaxy. Each base has to be on a portal.
Sometimes, I mess up and delete the last base in a galaxy. That means I have to pay the price of reentering the galaxy, which is done via the centre of another galaxy. That’s why I build bases at galactic centres.
Finally, no Man’s Sky has a limit on the number of parts that can be used in bases, overall. Thus the bases I build at the centre of every galaxy, are, for the most part, simple. It’s these bases I’m showing here.
Many players use a similar strategy.
Another aspect of the game is resources. One way to get most resources is to mine them. Thus some of these bases at the centres of galaxies are a little more complicated; they have attached mines, or whatever is necessary to acquire the resource.