Just faced a mostly Stealth team (4/5), and without any kind of helpful vision stealth can have way too much ganking potential
I know there is oracle vial, but at 250 gold and with such high death rates, it can be easy to go bankrupt especially if stealths begin to dominate
Just playing against stealth and seeing so many of your teammates die because an enemy champ swooped in behind them to kill them while capping a point from anywhere on the map (plus with the bonus stealths get from breaking it) is way too powerful.
With stealth champs able to hug your turret and with winning about capping points, it can snowball out of control, and buying bunches of oracles burn through your wallet. Stealths would still have control over the center, but now they can't just employ cheap tactics to kill u at those precious cap points