Why are people building Ravenous Hydra on anything that's melee?

Seriously, I've seen it on champs that would rather get a botrk to avoid getting kited and who actually use the AS(like Aatrox, Shyvana, Sion), on pretty much ANY melee AD Jungler even if the Jungler is behind (0/4 Lee Sin, better get that hydra FAST), on Zed, on Kha'Zix, on Pantheon, on EVERYTHING.

I just go to the point I dunno if the item is so darn broken/cost efficient and I'm missing it or people on drugs. I mean, it adds burst to some champs, but isn't it mostly great for splitpushing?