Wind drift for one. I shoot 160 Accubonds in my STW for that very reason........Due to the ballistic coefficient of the heavier bullets, they don't actually drop much more than the lighter/faster bullets.
The wind drift difference is negligible due to the faster time of flight of the lighter bullet. Take a 140 accubond at 3450 vs a 160 accubond at 3200, typical 7mm STW speeds, and the wind drift at 700 yds is identical at 28.5"/10mph x-wind, but the 160 gr will have dropped 8 more inches than the 140. I'm all for shooting heavier bullets if the game you're shooting needs it, but I've never failed to get a complete pass through on whitetails with a 140. I'd rather have the flatter trajectory. The superior B.C. of the heavier bullet will eventually cause the 160 to catch the 140, but that won't happen until after 800 yds and I don't shoot at game that far.
