This request came up again in the site design announcement which made us realize we never responded publicly about this. Sorry about that!
I think it wasn't totally obvious from the initial release that snippets are really only for JS/HTML/CSS code (a replacement for jsfiddle.net, basically). A good indicator of whether they'll be useful on a site is the number of answers with javascript in them, and especially posts linking to jsfiddle.
GIS I think is probably borderline for this, though you all are much more familiar with your community than I am. There aren't many questions referencing jsfiddle and the javascript tag also seems relatively small. I think we're looking at <3% of posts that could benefit from this (vs, say, Stack Overflow where it's more like 10%).
It's pretty easy for us to turn on (just flip a site setting) so the main question is not dev time but whether it's good for the community. Turning it on does come with some community cost as users get confused about the new button and occasionally mis-use it leading to weird broken code which needs to be cleaned up.
I'm leaning towards "probably not a good fit for this community", but if you all disagree let me know via a comment here.