Among the more well known frameworks are T3, Helix3, Gantry and Vertex. There are others but I'm sure you can find them yourself if you so desire.
The problem I have with all of these frameworks from the point of view of someone creating websites is familiarity. One customer wants a template that uses T3, another likes a Helix 3 based template and yet another takes a shine to a Vertex based template. Each of these frameworks has their own way of doing things and it and it can be a pita flitting from one to the other.
Perhaps another issue is that each of these frameworks is yet more code on top of the standard Joomla code. Adding more code to your website for the search engines to plough through is not top of my list for improving search engine optimisation. All this extra code, and especially CSS and JS can cause havoc on mobile devices stretching out the rendering beyond what is acceptable.
Interesting to see that Joomlaworks (the makers of K2)have revamped their template market/offerings and one of the plus points in their comments about additional code:
Our templates follow a simplistic approach: we don't use dozens of CSS and JS files. Instead, we only use 1 CSS file as base (2 if you choose to use K2), 1 CSS file for any custom styling you wish to do (custom.css) and just 2 JS files (1 for common libraries & 1 for the applied behaviour). This makes all our Joomla templates lightning fast to download & render on the browser.
Whilst I don't doubt that the framework developers offer up some very unique, impressive and special templates I do wonder if it's worth it and perhaps just relying on the Joomla core isn't better from the standpoint of the website visitor.
The irony is that this website itself uses a framework, the Helix 3 one which I rather like!