Without an easy place for spam to go It will go into more damaging parts of the system. The chain being less utilized will make the cost of a utxo spam attack more feasible. Rapid Growth of the utxo set will outstrip the normal configuration of cheap node hardware. The doomsday scenario for bitcoin is that a 16gb ram node can’t sync. All to save a couple dozen gigs a year of hard drive space. Makes no sense to me unless fed capture is the goal.