Some shows are episodic and work well with many episodes per season, some do better with fewer for a focused storyline. It really depends on the show.
I couldn't imagine The Last of Us having 24 episodes seasons. SG1 having ten episodes per season wouldn't be the same either.
I think the biggest thing is that sci fi shows have tended to trend fewer so they can have movie quality special effects make up a more significant amount of their run time which has caused costs to skyrocket.