Well, you wield the maul in front so it draws you forward, adding to your speed. So it has a lot good or - as we call it - freedom weight. The quiver is on the hips, so the arrows draw you down, effectively slowing you. That's because it's mostly bad weight. The ingame indicator only shows final weight, hiding the complex calculations(triple integrals) with the different weight types as parameters. So while the maul has of course more real world weight than those arrows, the ingame player pace determing weight is about the same.
I'm I profound yet?
The other reason is that 2h wimps cried so much that peasant archers could outrun them that we made arrows retardingly heavy to prevent another biblical flood (of tears).
