Probably because they have hundreds (if not thousands) of people working on OS X, and they need to "do something" to justify their paychecks.

It's the same reason that there's no longer a toggle for "Translucent menu bar" in the Desktop preference in Yosemite. Instead it moved elsewhere and does something almost the same, but not quite as good.

Or why they removed the "Dock" entry from the Apple Menu. They're showing that they're "improving" the product. But it's make-work, they're not improving anything.

I'm sure that all of these things were discussed for countless man-years in countless meetings. But Apple made somewhere in the neighborhood of $70B in profit last year, so it's not like they can't afford paying these people.

OTOH, all the silly bugs in Yosemite ... apparently there isn't enough money to pay good, competent people to chase and fix them.