Obviously at least some people think we do need a soft-sci-fi tag, because at the time of this writing there are 355 questions tagged with it.
However, I find the tag's description suspect. Here it is in full:
Soft science fiction is a term for works in the science fiction genre which do not apply a rigorous scientific model for the universe. It can also be used to describe work where the science fiction aspect is incidental to the story (the same story could be told without the science fiction elements).
The first part, "which do not apply a rigorous scientific model for the universe" is both too broad (most scifi discussed falls here) and also opinion-based. People do not even agree on what "hard" scifi is, much less about what counts or doesn't count as "not rigorous".
The second part, "it could be used to describe work where [...] the same story could be told without science fiction elements" seems opinion-based (who decides whether the story could be told with scifi elements?) and also seems to play with the question being borderline off-topic. If it's on-topic, what's the point in tagging it so that people know the same story could be told without scifi? "It's on-topic, but with a few tweaks it might not be"?
In short, my arguments against this tag:
- It adds nothing useful to questions.
- It's extremely opinion-based.
- It would apply to almost every scifi question here.
My arguments in favor of keeping it are mostly out of laziness:
- It's too much work to remove it, too many questions use it.
Edit: not sure how it plays here, but we decided against having its close cousin, the sci-fi tag. The relevant part of the decision:
[these tags] don't provide any extra information about the questions with them, so it could probably be edited out without affecting the questions
soft-sci-fitag seems to be used without any rhyme or reason, people tag all sort of questions with it that are completely indistinguishable from questions without the tag. It truly adds NO relevant information.