Adobe just didn't manage the pivot to web design very well. Dreamweaver had been run into the ground. So was Fireworks. And look at where Flash is.
I'd argue they didn't manage it at all. Almost all of the web focused apps that people think of were acquired as opposed to being developed in-house. Adobe (correctly) recognized that the web was becoming more important and they could play in that space, but the mindset for what these apps were designed to address missed the mark.
A web-focused IDE as opposed to a designer's tool that writes things for you are vastly different in terms of what these apps do and how they work.