I'm guessing you can survive without them but I doubt Ford would install a part for no reason. They will cut corners everywhere to save money unless it's absolutely necessary. Without it you'll have metal on metal spring/strut contact.
I was told by Steeda to remove these on the front to obtain the desired drop with their coilover kit. Currently have 250lb front springs with full adjustment leaving me with well over a finger gap. Their solution was going to a 225lb front spring and remove the "helper spring".
Swap takes place next week and hoping that I don't have any NVH issues.