Self-selection

The Universe contains a very large number of sapient species. But not all of them come to Space Station 'A long way from anywhere V'.

The Magma Men of Plodial 4 know that they would freeze solid if they tried to visit, so they stay away.

The Methane Breathers of Blubliblub know they would catch fire in an oxygen-rich atmosphere, so they stay away.

The Kiniggits of Galia know they would be poisoned by all the water vapor in the air, so they stay away.

And so on.

What you are left with is just those species that are water-based and oxygen-breathing, thriving at approximately the same temperature. Fortunately that is still a good number of species.

The Methane Breathers of Blubliblub and other places have their own stations where they meet only other methane breathers. The Kiniggits stay on their ships, and the Magma Men really doesn't travel much... Life support is such a hassle at 900 degrees centigrade.