Apps, Not Documents
As you might imagine from the name, the WHATWG is more interested in providing a display language for client-server applications than providing a format for documents. That doesn't mean that documents are completely ignored, but it demonstrates a shift in focus. HTML 5 is intended for things that are mainly going to be displayed online, while XHTML 2 described more static documents and was closer to something like DocBook than a modern web authoring system.
There are a few things that make this distinction clear. The most obvious is the <canvas> tag. This was originally developed by Apple for use in Dashboard widgets, but is now supported by Opera and Mozilla natively, and Internet Explorer via a plugin. The <canvas> tag provides a 2D surface onto which scripts can draw. You can use this to embed static 2D images that are drawn by scripts, but more commonly you'll use it for generating dynamic displays.