I think it's because so many space games try to dazzle with the unfettered dream of exploring the endless cosmos. But you obviously can't fill an endless cosmos with interesting things to do. Hell, most of space is just dead rocks and hot gas.

I feel like dyson sphere program is somewhere further, it being a sandbox factory game means you can do basically as much as you can reasonably handle on your computer, although story wise it's not great since it's not meant to be a story game