>I'm asking why they don't recognize that a portion of the answers they provide will be useless without being able to solve simple math problems.

?? They absolutely recognize that it's not good at math. It's not meant to be good at math. If you're still using it for math despite being told it's not good for math and despite the obvious results showing it's not good at math, then that's your problem, not theirs. That it's not good at math hardly negates its core competencies, which are remarkable and highly valuable.

>They could certainly build in a calculator now

What? That would be absolutely pointless. They might as well just tell you to use your own calculator. In fact, that's what Bing Chat would tell people if you asked it to do a math problem back before they neutered it.