I'm with you 100% here, but I'm also 100% with sibling jiggawatts.
To me, Mathematica is a computation environment that conveys a Lisp Machine feeling of "the machine and I are working on this problem".
You know, that "assembling things live in the sky" Lisp feeling (Yegge's phrase, not mine).
The only other computation environment that is right there en par in flexibility and conveyance of the same trippy feeling is, of course, Emacs.
The company can still make money from academic and professional licensing and support contracts, and everyone else gets to have access to an awesome thinking tool as a matter of fact.
They've already gone that direction a bit with the Raspberry release, what's left now is just the final push.
So, if Stephen Wolfram ever reads this:
Open source Mathematica and it will have a chance at immortality.
Just like Lisp and just like Emacs, and the people will rejoice.
Disclaimer: I started with Mathematica 4.0 at age 14 (a pirate copy too, sorry!), turned on by that marvellous column in Quantum. But I was put off precisely due to the proprietary nature, and switched to C and Lisp. Consequently I became a CS guy rather than a Physics guy, because C and Lisp were accessible early on, while Mathematica wasn't (legitimately).