AH YES!
The good old actual atmo. Planets

They are INDEED the No.1 answer to this question, and as was stated countless times before;
SHOULD FDev decide to do them instead of Ship Interiors, FINE! No complaints!
Thing is: They would be SIGNIFICANTLY more work while simultaneously SIGNIFICANTLY harder to monetize.
Simple as. That makes them the OBJECTIVELY less logial step to take.
Yeah yeah. The good old "It's just your opinion." - card.
Everything is "subjective" according to that logic.
But in reallity it really isn't.
I know the difference between the two well enough my dude

You see, there are such things as "arguments".
Arguments are the core basis for any form of discussion.
If for example, someone is in favor of Stance A, and his only argument is "It wOuLd bE AwEsOmE!"
And then someone else is in favor of Stance B, and he lists a plethora of logical arguments covering every potential field,
while simultaneously debunking essentially any and all counter-arguments, well then Stance B can 100% be described as OBJECTIVELY better!
And guess what: Stance B is 100% the case for Ship Interiors