> But there is a reason we don’t use monospaced fonts everywhere. They are somewhat hard to read because [...]

Well, not sure what is the basis for that assertion, but I find it easier to read text rendered in a monospaced font (Courier is my favorite). In fact, when I need to read something longer than a minute on the browser, I switch to monospace (with help of a browser plugin). It's not about text alignment -- it does not matter when reading prose, but perhaps about the familiarity of a font.

As an aside, I also try to get rid of formatting when reading long text. It allows me to focus on the essence of the written word. Perhaps, this is why the old school mailing lists and message forums are more appealing than the modern crop of social media apps. Also plain text email (what a rarity in the corporate world today!).