If you're adding an item that doubles as Bond of Stone, why remove Strength of Ages?

Strength of Ages is a very powerful mechanic for late game tank champions. Why is it getting removed at the same time that a new item will have a built in Bond of Stone passive? Shouldn't they remove Bond of Stone instead and just shift the utility towards the item?

Edit: Adding this here in case anyone doesn't know what I mean http://na.leagueoflegends.com/en/featured/preseason-2017/gameplay#masteries