Umm... seeing as the holiday events take very little effort to develop? Nope, not a waste at all. It's not taking anything away from the development of other content.

You ever heard the expression, "Too many Chefs spoil the soup?"

They can't and don't have EVERYONE working on the same content. So those that can't work on one piece of content are free to work on another.

Besides, the seasonal content was already planned at release, so again your point is moot.