Why can Draven rush bloodthirster or DD and still do as much damage as a mid game ADC with two items

just wondering how most ADs need to either build a zeal item or infinity edge to stay relevant with damage as enemies accumulate more health and armor but Draven rushing bloodthirster or DD doesn't affect his overall damage out put and gives him stupid early amounts of sustain so that he bruises HARD and has no penalties for attacking head on?

also, my personal opinion on his passive: any passives that give an increase in gold by any amount are really, REALLY, stupid and give ridiculous laning advantages.

Draven mains aren't allowed to comment due to the following: -arrogant -will be biased towards this post