OP never said he wanted an alternative, just expressed surprise an alternative/competitor didn’t exist.

I know. I just picked on it because on one hand it is great that Wolfram was able to execute on his vision and make it work as a viable product. It needs a lot of resources to make something as great as Mathematica. On the other hand, an essential tool like that, you want to own it for life and grow with it, and I don't think that is quite possible with a "product".