Your failure in reasoning here is assuming that all of them are purely and only language models. That they receive no other source of learning other than language models -- for example, they aren't fed any kind of pop science math.

It's clear that this is true of models like ChatGPT, but isn't the Bing thing powered by GPT4 with a number of other enhancements? Fixing this "can't do math" thing is a low-hanging fruit for development improvements.