Because some of these critiques really should have been dealt with beforehand and I'm concerned that we're now stuck with lousy defaults that they won't ever be able to change.
The visual font size problem seems particularly disastrous:
> The math font is a really small,
> MathJax’s default font MJXTEX-I and GitHub’s default text Helvetica have a different x-height/cap-height ratio.
I don't understand how Github could launch this feature with this problem unaddressed. LaTeX isn't just about getting formulas right, it's about communicating ideas.