many “unused” IP addresses are unused because they’re kinda like having spare parts: if you’re planning on extending your network in the futures, your IP block kinda should reflect your end state (ie the parts you need over time to replace or “build” new hosts)

or for blue/green deployments where it’s likely that at least half the IP range will be used in terms of process, but unused most of the time in terms of reachability

and then there’s weird things with splitting up IP blocks into subnets with a division of 3 (the minimum needed for dealing with net splits etc) - eg across availability zones… there are always “waste” IPs because you can’t divide multiples of 8 cleaning into 3