If you ever switch to Conquest it is a really strong item. Stacks are much easier/ more efficient to build in Conquest. A lot of supports/tanks will build it early.
Multiple T1 will give you smaller boosts for multiple stats which will be less impactful. Building T3 will give a higher boost for specific stats which will make you more impactful.
It’s the same reasons why you would generally level up your strongest, best abilities first instead of leveling everything up equally.