Because Barbarians are melee and strength characters. Their ranged weapons of choice would be javelins and spears (or other versatile heavy thrown weapons).
what encounter powers I can steal from Barbarian for heavy thrown weapons. It sucks that rangers get really sub-optimal Heavy Thrown attacks. Quick Throw is kind of...why?
If they're gonna support heavy thrown weaponry they need to...you know, support it. I don't even know of a single class that actually favors this fighting style in a good way (using Str as the attack stat).
Seriously, a hand ax is heavy thrown and uses Str, except when you're a ranger, or whatever. The rules don't make sense. Another reason why Essentials are better designed, though weaker. With powers that key off ranged basic attacks, it is possible to use Strength and heavy thrown weapons with multi-attacks. (I think)....I'll ask this in another thread.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.