I believe such a resource would consume a lot more from SE servers, your questions reminds me of one question I've found in the philosophy.SE meta asking about the implementation of $\LaTeX$ for them, the answer was as follows:
Currently, only a handful of sites on the Stack Exchange network support LaTeX notation. Implementing support has been requested for some of the other sites, namely Stack Overflow, but has been denied.
The official argument from the team is that supporting this is an extremely heavy dependency, and that parsing LaTeX equations is an extremely expensive operation on the client side.
Certainly for sites like Mathematics where it's absolutely necessary, the massive dependency is an easier pill to swallow. And on sites like Stack Overflow, where it would only be used in exceptionally rare cases, it's a much easier decision to deny the request to support it. But on this site, I think things get much trickier. While there will be some questions dealing with formal logic that will require such mathematical-style proofs, there are also a lot more questions that deal with more abstract concepts which words will express just fine.
If $\LaTeX$ was denied for them, I believe such tool for graphing would also be denied for us because it's possible to use an online alternative such as W|A, FooPlot or Geogebra for free and when it's not available, we can upload images.