Because there's a value proposition. Just like TCL, Perl, and Lisp had value propositions over other available languages. It's fine if you don't see the value proposition in Crush but progress sometimes forces us to learn new things instead of sticking with what we have.
If I’m being honest, you’re not adding anything constructive at all here - it seems you’re in a competition with yourself as to how much you can degrade Crush for whatever reason.
You act like it’s a choice between Crush and Perl. People don’t have to learn Crush. People don’t have to learn Perl. Will picking between the two have any substantial effect on one’s career outcomes these days? Probably not, as candidates will have already learned the important languages for getting a job anyway.
But it is cute to couch it in a complaint about not being constructive; points for shamelessness.
By that logic no one should make anything new to replace the incumbent.
In case of Perl, PHP came and it replaced Perl as mainstream web development language.
In sysadmin stuff where Perl used to be mainstream, now significant chunk is taken away by Python.
These days JavaScript appeals to younger people more. Times change and with it the tools people use also change.
There is no guarantee that any new project will succeed but you won't know unless you try.
You're really bringing up a separate point which is "should we be reinventing the wheel?", I think that's a fair point, but it's not a response to the original commentator.
There are more young people who know Perl or Tcl or Lisp than know Crush. I've never understood this reasoning - "Hardly anyone knows X. Let's replace it with something nobody knows." At most, you're making an argument about a lack of sunk cost.
> May be some "new" shell will catch up and tomorrow's "all" programs will be compatible with that shell
Think of it like transitioning to life in a wheelchair. You can't "catch up" with your house - it just wasn't designed for wheelchair use. Renovating all the narrow corridors, random steps, tight angles and vertical reaches probably costs more than rebuilding.
In this comparison, the mobility mode is your shell.