Why are Web 2.0 tools separate from each other?

I like blogging, now that I've tried it. But it bugs me that blogging software just does blogging (and wikis just do wikis ...). If I want to upload some files to the blog, like I can with a Google Group, I can't do it. I also can't email to it. If i want to collaboratively edit a single document, I need to either go with a wiki, or sharepoint etc. It would be nice to keep all the files, emails, notes etc associated with a project in one place. Groups are pretty useful, and they have a kind of simple blogging function, but it isn't as good as blogging programs. Not as sophisticated, and fewer features. Wikis seem nice, but the formatting available is not nearly what a Word file would give you.

If only all of these Web 2.0 things were built out of smaller widgets that could be inter-combined at will.