Collapsing trunks have been a thing since the 90s.
There's no regulatory requirement for crumple zones. There's regulatory requirements for performance. The cheapest/easiest way to meet these is crumple zones.
Your luggage and golf clubs aren't gonna do squat in a collision. The regulators don't care that about the one in a million chance that someone gets into an accident a) where crumple zones matter b) while hauling objects so solid they don't just round to "no effect" because they have bigger fish to fry and if you create a "standard loading" for the test the OEMs will simply design to that and basically create a bunch of work and expense for marginal benefit.