I have heard that to be the reason that some don't want to "fix" TeX/LaTeX.
Source: http://en.wikipedia.org/wiki/TeX#License
LaTeX also has a similar clause (or whatever you call it): http://en.wikipedia.org/wiki/LaTeX_Project_Public_License#Un...
> To enforce this rule, any implementation of the system must pass a test suite called the TRIP test[39] before being allowed to be called TeX
A lot of people have thought about rewriting (parts) of TeX, but the amount of legacy is so high and you have to keep compatibility with lots of existing user code.
I'm thankful for anything that helps to free us from the *TeX compilers. It's surely hyped too much. Do you believe me when I say that just because you wrote a document with LaTeX, it isn't auto-magically typographically perfect? Look for PDF Documents compiled with LaTeX, many of them have really ugly Typography, because people love to customize things to their own likings and many LaTeX templates even force ugly Typography on their users.