What's the use of the science tag, given that one might expect most questions on this website to be related to science?
There are only 14 threads tagged with science. I looked through them and I don't see anything in common among these threads. It appears to me that this tag (that, by the way, exists since 2010) is being applied without any coherent system and hence does not serve any useful purpose.
I would suggest getting rid of this tag.
Update (Jan 23): I have eliminated the tag.
While I don't have figures to support this impression, personally I wouldn't expect most questions to relate specifically to science; a large fraction, certainly. (However, I think that's not really the issue here, aside from suggesting that the tag is overly broad, which may be the case even if it isn't anywhere near to a majority.)
There's potential value in a
science tag if the tag is used to indicate a set of characteristics of the work being asked about that are common in science but (almost) absent elsewhere. These might include things like known functional forms, and measurement errors of given size on some variables.
However, such common characteristics of science-related questions may be better handled by more specific tags that relate to those characteristics; I suppose there's some tension if that leaves too few tag-slots to describe the features of the question itself.
It might be worth going through and seeing how it's actually used -- is there something about the way in which it's being used that makes it worth keeping?