The Death of Wriggle's Junglers

[Kaden]

It's a matter of making your worst-case scenario as good as possible. The bruisers (with Olaf being pretty close to an exception, imo) need items to really be able to do anything. Olaf and Nocturne can dive into the enemy team, but unless they've got a good amount of gold, they just get blown the hell up.

If you pick a tanky jungler who can jungle just as well/better than a bruiser and buy gp/10, you're guaranteeing yourself gold income even if you get counter jungled or you can't land ganks. That really goes back to why tanky DPS was such a frustrating meta: champions can keep good DPS with their abilities while itemizing for tankiness. Maokai and Udyr are pretty much the epitome of that.

The other thing that tanks bring are the power of their skills. Pretty much no one ganks as well as Maokai because his kit is just insanely good for it and also comes with a massive damage debuff for the enemy team... that also turns into damage. Skarner is such a powerful initiator that when he does it, the other team just gets to lose someone for it. Bruisers don't get to do shit like that.