> symPy ?

Uhm... it says right at the top of the linked website that sympy is used as the backend.

True - but the question stands. Why use it in the Mathematica way/syntax than by itself.

Remember I'm not qualifying the value of this project as a replacement to Mathematica. I'm asking who is the segment bthat would use this as opposed to going directly to symPy or R.

I think you're right that Rymbolic + sympy are good comparisons as well.