I selected no and I think for those developers who have selected yes are quite the fools on this post at least. I come from HTML 4.0 and CSS 2.0 when we didn't have CSS frameworks.
It does help if you know how to write in CSS from scratch but when I returned to the market the last few years CSS frameworks were a new thing to me and this caught me by surprise! It's taken me awhile to get my head around the whole lot of it but there are so many new elements have been introduced, as well as CSS becoming a lot more semantic with stricter ruling.
Back in the day you could easily write in CSS but now if you're writing from scratch and using your own code, well you soon learn that your code keeps breaking.. Can become quite annoying, hence why they have also now created CSS tools and plugins which will inform you if your code is wrong CSlint, there's a few of them in different languages.
I still prefer writing my own code but if I was to be hired then I would opt for a CSS framework simply because it will be already optimised, a lot more functionality and it's much faster to deploy a website or web application with a pre-built framework.
I would alway, always keep trying to practice CSS in your own time but at the same time when you're going professional, use a framework, less cost and less time :)