Thanks for asking :-)
Because Microsoft has exclusively reserved yellow text for banana and lemon related topics, just like red is only available for strawberry, raspberry, and cherry related ones. Try using Apple Pages or Google Docs...

Seriously ?
No, of course not. It's just a matter of not enough contrast with its background color, like Elmander Elmer already answered.

Oorspronkelijk geplaatst op Quora: Why is it hard to see yellow text in a Microsoft word document?"