Because D&D and its derivatives are medieval fantasy, and they're the most popular games by a huge margin. Take those away and the most popular settings are Star Wars and WH40k.
Medieval fantasy is the go-to genre for most TTRPGs
Josiah White
Colton Russell
Elves in space have the benefit of coexisting with tons of other modern (or futuristic) creature comforts.
Lincoln Collins
It's only cyberpunk if you decide to have corporations or the government ruling everything with an iron fist. Sci-fi doesn't automatically become a dystopia just because you can't hop over to another planet without worrying about any problems at the last one.
Lincoln Rodriguez
How do we fix this autist problem?
Elijah Torres
so more gundam than star wars?
im ok with that
Aiden Roberts
You are correct and not wrong.
But reality is that most sci-fi setting that focus on a single planet usually is cyberpunk in nature.
Brandon Taylor
Just ignore it?
There are room for everyone and all kind of genre.
Jaxson Hall
I'm honestly surprised that Shadowrun is that high up.
David Clark
The obvious solution is have problems that can follow them.
I get the issue of your ship blowing up just being random TPKs though. Perhaps find a mechanism by which the primary form of ship combat involves slinging them into the atmosphere of planets, forcing a crash landing and ground confrontation? Feels arbitrary but I'm sure there's a way to justify it.
Jose Nguyen
A medieval world is roughly easy to predict.
A sci-fi world has to many common possibilities
>Surveillance
>Instant long range communication
>Mass production of powerful and complex devices
>Extremely fast travel from one location to another
>Incompatible software/incomparable technical skill sets
>Powerful, precise long-range weaponry
>Fucking surveillance
and that's just our world before factoring in teleportation, functional AI, super-fuels, nano-machines and a whole host of other crazy bullshit that may or may not exist.
A GM has to know what does and does not exist and how it interacts with whatever else exists in a logical way. The players has to be able to anticipate what they might go up against at any given time.
Most really popular sci-fi adventures ignore security cameras almost entirely. 40k ignores most meaningful sci-fi tech all together. Dune lacks computers and still ends up crazy complicated. Starwars may have hyperdrive, droids and lasers but in practice it winds up being effectively fantasy WW2.
Technology is fantastical but what makes it a problem in terms of building an open game world is that it's common. Sci-fi is a world built by wizards. As crazy as D&D can get it is spared the fact that all in all wizardry is rare enough to be recognised as such. Life is normal until you encounter a spell or an enchanted dungeon or the magic-man himself. But otherwise life is somewhat predictable.
In a sci-fi world magic permeates life to the point where it, usually, isn't noticed anymore. Finding a way for that world to exist without flying apart the moment a PC touches it is no small feat.