Because fiction doesn't evolve through "making room", but through the opposite. You get stories by closing some of the infinite paths, by debunking some of the possibilities, and by slamming the door on some of the might-have-beens.
Once upon a time there was a little girl whose name wasn't Julie, Rachel, Geneveve or Kathy. Her name definitely wasn't anything but Goldilocks. One day while not skipping, not running, not jogging or shuffling languidly through a wooded area that was definitely not a national park or forest preserve but was in fact an actual forest and nothing else, she encountered a wooden cottage that was not more than one story high and had fewer than five windows. It lacked nameplate that might have identified its owner, and it lacked a second chimney, but it had a first chimney through which smoke was not failing to emerge. The girl whose name wasn't anything other than Goldilocks smelled something delicious coming from that house and said to herself "I definitely know I am not supposed to enter that house and I can narrow down my motivation for breaking into that house as being attracted by the smell of the food inside and I know for sure that food is porridge and not anything else so no one should ever need to speculate on why I am now braking into this house with no nameplate so I don't know that it is owned by three bears..."
"Space. The final frontier. These are the voyages of the starship Enterprise. Its five year mission is NOT to host circus performances, bring toys to children, rescue stranded astronauts from traps caused by ancient still-working alien technology, but we still do those things in a pinch, even though they are not our mission. Also, to explore strange new worlds, but not worlds that have no atmosphere or aren't earthlike, or that reside in someone else's territory, or that are ugly or smell funny, or that we've been ordered not to explore, or are not strange enough that we find them boring. To seek out new life and new civilizations, just not Category 4 civilizations because those are really dangerous, and not civilizations that don't like us, or civilizations that time travel because they're scary and weird. Also, to boldly go where no man has gone before, though not ONLY where no man has gone before, and not excluding where man has gone before but lost the records to so we don't know he's gone there before, and also not excluding starbases, vacation planets, cheesy bars on harbor planets and other places where men have definitely gone before but we will not rule out going there because we also sometimes go places where man has gone before."
Yeah, I'm not really buying it.