Look, the difference here is not just that one thing is “celebrated” more than another. It's that one thing really includes people in a meaningful way and the other thing (publishing a book, getting PhD), does not. It's very neat to get published; it's also unlikely to change the lives of the people around you. On the other hand, becoming a grandfather certainly will.

The original poster is missing what's truly going on. Babies are new social connections--deeply, universally relatable and inclusive emotionally, socially, and materially (hence baby showers. You directly contribute to the well being of new life). Her PhD isn't any of those things. Of course the enthusiasm is lopsided. It could hardly be anything less.