Heavy ammo glitch. Think about it. How many players out there using the heavy ammo glitch on Skolas in POE? Now those who have used the glitch, imagine if it took 8 seconds per round generation? That would make it very difficult if not impossible. Especially with the way adds keep spawning and how soon your primary ammo returns. I suppose Bungie couldn't figure out how to get rid of the glitch/cheese without causing more bugs to occur in the game so this is how they discourage it.