It's not hard to see why DJI would make this particular upgrade mandatory. It doesn't want to risk even the slightest possibility of a drone injuring people as it crashes to the ground. However, this is bound to be slightly disconcerting if you're an owner. Effectively, DJI has full control over whether or not your drone works. The company isn't likely to abuse that power (it has strong incentives to keep you flying), but it gives the impression that you don't really own your drone -- you're just paying for permission to fly it.