This, in my opinion, is why frameworks of any ilk exist at all. Too many developers out there don't want to take the time to learn the language and the frameworks give them a (false, again, my opinion) sense of productivity.

But, especially with CSS, I really don't see the value provided by a framework. CSS isn't hard to learn or master! And as OP suggested, doing so means you get more done with less code.

I know a guy who set up a project with a framework. He had a nice scaffold of the project and was amazed and overjoyed with what he had done with so little effort until it was pointed out to him that he had 40,000 files in a project that didn't actually do anything. Much less solve the customers problem.