Even if you managed to up the draw wt. the up the arrow wt. and the speed stays the same, you've still gained so much more energy and forward momentum in that arrow. So for now, say your getting pass through on deer sized game, increase the wt. 10 more pounds, increase the arrow wt. 100 grains and your getting pass throughs on any game in North America.
See the benefits?
It's not so much about speed, but how fast can you push a heavier arrow, now your literally making forward progress.
That's why I envy the guys who can still shoot 60-70 pound bows. At one time I could shoot 80# bows all day long and hunted with an 80# bow for years........my arrows were 600+ grains and the energy produced was unbelievable. Man I wish I could still do that!