There is an argument that claims that the reason some or most people switch during their childhood from a natural forefoot running into an unnatural heelstriking form is because of high drop cushioned shoes. I think it's not the high drop that makes them switch to heel striking, because we see people running with high drop cushioned shoes, yet still forefooting. Also if add all three factors that makes you strike forefoot-relaxed foot, forward lean, and landing on a bent knee- you would get an angle of the foot that will allow you to strike forefoot even with a very high drop that can't be found in any running shoe. So I say it's an inflexible sole that makes one change the striking pattern. A stiff sole doesn't allow the ball of the foot to take the impact- thus forcing you to switch to a more comfortable pattern of heel striking and rolling on the foot instead of a springy forefoot pattern.
https://sc01.alicdn.com/kf/HT1JTDIFIlXXXagOFbXP/200641131/HT1JTDIFIlXXXagOFbXP.jpg
Ever tried forefooting with a shoe like that?