[agalunar]

[It's also worth pointing out that Computer Modern was not created as a demo, and in fact, it's almost the other way round. He wanted better typography for The Art of Computer Programming, and created TeX and Computer Modern as means to that end (and created Metafont in order to do that).]

[Chris_Newton]

It’s also worth remembering that CM was designed with some very specific goals in mind in terms of clearly distinguishing a much broader character set than was the norm at the time, even at very small sizes. It is still arguably the most successful font family ever created within its intended niche. Very few font families can be used to typeset serious mathematics as legibly as CM, and even then, few authors will make the effort to set everything with the attention to detail Knuth has.