Probably because Microsoft knows vibe coding is _not_ an actual viable way to build production ready code and does not want to deal with the liability issues of prompting customers to move from a working Excel sheet to a broken piece of software that looks like it works.

In my experience, it's actually quite hard to move a business from an excel sheet to software. Because an excel sheet allows the end user to easily handle every edge case and they likely don't even think in terms of "edge cases"