Not many resources perhaps, but a lot of additional UI surface, which clutters up the menus with irrelevant options.
Is there a cost to adding even a button? Yes. But that has to be weighed against the benefit. And a significant amount of users benefit from having the button.
In this case, data on user behavior indicated that it was worth adding the buttons. It's still possible that the data is imperfect somehow and a more optimal tradeoff could have been chosen. Still, I think there is good reason to believe the current data and decisions make sense.