Because it’s not that deep and the realm of the possible shifts differently for scientists and writers and the general public. For a lot of people science fiction is defined by tropes and trappings but not so much the possibilities. For instance when I was a kid Star Wars was still considered sci-fi because it had lasers and spaceships. For a lot of people that’s all sci-fi means. But language evolves and so does our understanding of what a genre should include.

Like my favorite novel accelerando is about the singularity, a concept many nerds were interested in about 20 years ago. These days we’ve all kind of accepted it’s a silly thing that doesn’t make sense but does that mean we should reclassify all of the fiction written around it as a concept as science fantasy? At one point tech has advanced to the point where they’re cloning humans so cheaply that politicians are cloning multiple versions of themselves to go campaigning. Does this impossible scenario make those books science fantasy, even though they get a lot of the science right elsewhere? Because if the answer is yes then we’d probably need to rename all sci-fi sections in bookstores to science fantasy because that’s the majority of what’s in them: fun shit with a veneer of science behind it.