I don't think that's a problem, personally. Something like canvas
should be an all-or-nothing proposition. There's very little overlap between what you need for content-based static web pages and applications that just happen to run on the web.
The problem is canvas wasn't designed to be that all-or-nothing alternative to the DOM. It was designed as an alternative to the flash player for html5 games. As a result, it lacks several features that are needed to display generic content, the most prominent of these features being proper (and easy!) font rendering.
I suppose you could build your own advanced font rendering engine (I think Flipboard did exactly that), but that's more work and risk than most companies or even individuals are prepared to take these days. And you are right; creating your own would cause you to re-create a lot of stuff that's already handled by the browser, like font highlighting, copy/paste, etc.