I've always wondered ever since I've started League, as to why you have to build jungle items at all. Can't Riot just put the bonus xp and bonus gold into smite itself as a passive and just make it so that junglers don't have to buy hunter's machete or whatever?
was added in season 3 so that junglers had a buyable item that helped them clear, but maintained difficulty for champions who would forego a jungle item for raw power in ganks early on.
It was better when it built into items (see: Spirit Stone/Madred's Razors) that weren't jungle-focused versions of general items (like 
is to 
, for example), but that's the reason it exists. A gold-efficient item for a role that (with how it's supposed to be designed) has less overall gold income than the laners.
That's how it used to be a long time ago. One of my favorite starts jungling Trundle used to be a vamp scepter and 2 red sodas. However, cloth armor + 5 reds used to be the safest start.
IIRC they added hunter's machete to help diversify the jungling roster a bit, because surviving the jungle used to be a lot harder back then. If you messed up back then you would stay behind for most of the game.
Today's jungle is practically casual mode in comparison. Champs can now gank repeatedly and camp lanes with zero consequences. Resource managment is barely a thing, since jungle items come with both health and mana sustain. All the planning/strategy goes into champ select rather than decisions made in-game.
