To sum up why does a throwing knife deserve to have accurate when most of the rilfes don`t?

As Jargal round-aboutly said: because the rules aren't there to model the real world, they're there to model genre fiction. In this case genre fiction where assassins with throwing knives are kick-ass.

That's all well and good but, when you aplly it to a game with a ruleset inherently designed with a view toward balance, it kind of falls flat.

If you want your knife thrower to kick ass, upgrade his BS. At the end of the day a knife doesn't deserve the same accuracy bonus as a hunting rifle.

The rest of that statblock aside, in this case, Accurate is only going to give +10 to hit. The extra-damage-for-more-DoS thing doesn't proc except with Basic weapons - all of which are ranged and rifle-sized.