The only place where I have found wider bars to have a handling advantage is in high speed off road riding across rough ground. Wider bars make it easier to resist the front wheel deflections caused by ruts, rocks, tree stumps, etc. and thus control the direction of the bike. Even so, the effort to turn in rough going is fairly low and doesn't require much leverage.
Back when there were more unpaved roads, street bikes needed wide bars, nowadays, except for adventure bikes not so much.