Because it uses OpenStreetMap as a map source it doesn't show any settlements larger 250,000 for my area because those settlements call themselves "towns" and not "cities".
When you zoom out all you see is a blank space with no labels for quite a large area of the screen.
Meanwhile very small settlements (< 20K people) are shown at max zoom just because they happen to have the right kind of church building, which in the UK means they can call themselves "cities".
I've raised this issue with OpenStreetMaps support for many years and they just either say it's something to be fixed by client libraries or it's not important.
They could be right I guess. However, Goople maps, Apple maps and Microsoft maps handle this correctly and that's what OpenDesktop explicitly say they are trying to replace here.