Yeah, other components are much more useful for building the average channel, but that's because they do a lot of the work for you. But since they do, they are somewhat limited in how you can use them. I wanted to pick a component that I could stick with and continue to use for most if not all the tutorials, and just throw extra components in as needed. Some of the more complex components would have fit the bill, but they have their own specific complications. The ImageCanvas is unique in my mind because it is a very simple component (see tutorial part 1), but can be used in very complex ways (e.g. KidPaint).
I think the confusion may be in the fact that you're writing BrightScript programming tutorials, rather than Roku channel development tutorials. I just think you need to be clear about that, possibly by stating that in your intro, otherwise new developers may not realize that most of the standard components do all of the (non-graphical) UI work for you. 90% of new Roku channel developers will want to use the built-in components to develop their channels, rather than the image canvas.
This isn't intended for those intending to just take an example channel (of which there are many in the SDK) and alter it, but for those struggling with the core concepts of the language, or that have trouble following what's happening in the examples provided.