More accounting profit, not economic profit. You have to earn a return on all the additional assets you have by going vertical. The Street will punish you if y

More accounting profit, not economic profit. You have to earn a return on all the additional assets you have by going vertical. The Street will punish you if you just buy companies to make more "profit" but your return on assets decline. Real reason is probably tweaking designs to their needs in a way that competitors can't access.