On Mar 10, 2022, at 8:44 PM, Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp> wrote:

IIRC, at some time, perhaps when CIDR was deployed widely and
having something other than IPv4 was a hot topic, there was a
discussion on releasing 240/4 in IETF. Reasonings against it were
that the released space will be consumed quickly (at that time,
NAT already existed but was uncommon) and that new IP will be
designed and deployed quickly (we were optimistic).

Masataka Ohta