As Nome explained, pre-spawn objectives determine starting bush positioning. Lower elo players don't understand or have the opportunity to develop for value what those objectives are (because they can't jungle effectively without a max setup), so they simply just steer towards map control (the most center point).
At higher elo, the bushes next to the jungle spawns are usually camped. However because the jungle creeps in Twisted Treeline were never updated like they were in Summoner's Rift (they made them easier to kill, and gave large creeps sustain buffs when you killed them), jungling is significantly more difficult. Without a full set of runes, masteries, and a very specific character, jungling is impossible; and thus irrelevant.
Just my 2 cents; I've been +1700 both seasons in 3's; started last season 14-0 in ranked 3's, 12-0 this season.