Four years is not really a very long time in the greater scheme of things, the pace of modern web development just makes for an impatient populous with short attention spans.
I don't think that you can compare a backwards-incompatible change in a low layer of the stack that runs the internet with a feature of CSS parsers that was standardised 4 years ago. Some things are expected to take more time than others.
Four years is not really a very long time in the greater scheme of things, the pace of modern web development just makes for an impatient populous with short attention spans.