Having recently become a convert to Grid Layouts, I find myself looking at more and more sites' code and seeing that grids are still grossly under-represented.
While I accept that grids might not always be the only right solution for every web design situation, I think that they are a tool that should be seeing higher rates of adoption than they currently enjoy.
I think if I'd known more about the design approach earlier, I would have saved a considerable amount of time and effort. But Grids don't seem to have the sort of exposure that, say, CSS standards do. Why should that be? Is it even a problem that some people might be missing out on a design approach that could potentially be a better solution to a problem they're working on?
The "Grid Layouts" you speak of, are nothing "special". What you are actually talking about, are "CSS frameworks". These "Grid Layouts" should still be using CSS Standard
You also did not mention the most popular CSS Grid Framework - YUI Grids CSS
I think the reason people normally don't use a framework, is that they don't want to be locked into something with limited customization. Also a big reason is that there is no guaranty that the framework will be around forever, and once it is gone, your knowledge with that framework is useless.
There is also some Criticism of CSS Frameworks on Wikipedia:
Also I think that most web developers just like to write there own HTML/CSS.