I forgot where I read it and the exact reason and I can't find it for the life of me. So this might not be that useful. I read that the better quality headphones are quieter than cheap quality. I don't remember if it had to do with the drivers, drawing more power, or frequency range or whatever, sorry. But I remember reading that. I know when I had the big over the ear Skullcandy ones the max volume was loud, but not kill your hearing metal band loud like I wanted. (btw skullcandy are cheap plasticy pieces of junk, I don't recomend them at all. The bass sounds cheap bad and synthesized punchy. And they break, cause they're cheap plastic.) I had 20 dollar sony ones that were much louder.
But as for the Droid volume, my Sony
MDR-EX36V earbuds volume leave a lot to be desired but sound great and give awesome lows. But my Sony
MDR-V6 are pretty damn loud. Maybe you're more deaf than me? Haha.