At least some of the blame here is the bias towards HTML being something that is dynamic code generated, as opposed to something that is statically handwritten by many people.

There are features that would be good for the latter that have been removed. For example, if you need to embed HTML code examples, you can use the <xmp> tag, which makes it so you don't need to encode escapes. Sadly, the HTML5 spec is trying to obsolete the <xmp> tag even though it's the only way to make this work. All browsers seem to be supporting it anyways, but once it is removed you will always have to encode the examples.

HTML spec developers should be more careful to consider people hand coding HTML when designing specifications, or at least decisions that will require JavaScript to accomplish something it probably shouldn't be needed for.