> Why should he?
Kaz invested a bunch of time implementing a whole new backquote implementation for CLISP, but it's still not good enough for him to use CLISP to implement TXR? It doesn't make any sense!
Any right-thinking programmer should care about inconsistencies such as this. If I'm evaluating a programming language, and I see someone in its community writing their own language implementation to support an application that could've easily been written using one of the standard language implementations, then it looks to me like the standard implementations aren't mature enough or trustworthy enough for me to use for my application. Not only that, but it suggests that maybe this particular language isn't as good as its advocates claim, especially if I have to drop back down to C in order to meet certain requirements (e.g., portability, speed, wider understanding, etc.).
But any right-thinking programmer already knows that lisp is not worth wasting any time on. It's dead, and people like Kaz, and projects like TXR, are going to make sure it stays that way.