As for why they still own it places like Amazon which hoover up large deaths of space like this must not have made interesting enough offers yet. GE sold 3/8 that way in 2018 for example.
They got it back in the day (prob mid-90's) because they asked for it - IP space used to handed out like candy on Halloween.. Now that it's a valuable asset - they are very unlikely to just hand it back.
This. I would always ask for a whole Class C when I needed one IP. A Class C was worthless in the 90s. Just like you could buy any dotcom domain you wanted. And mine however many Bitcoins you needed in 2010.
https://en.wikipedia.org/wiki/List_of_assigned_/8_IPv4_addre...
The United States Department of Defense has 14 /8 blocks.
(My judgement is, no doubt, clouded by the fact that, for the size of companies I work with, a /24 would be an embarrassment of riches.)
You can only use /28s and whatnot when you are using someone else's (usually a carrier's) addresses as part of a larger group in a single route advertisement. In such setups reviewing your DMZ logs probably requires looking at NAT logs, your entire outbound NAT pool being shared amongst all types of traffic, fun with peer ranges causing the block to get blacklisted, and similar friction as a result.
I deal primarily with small businesses who might host a VPN to facilitate access to on-prem systems, perhaps a web server for on-prem web apps, and in the past perhaps an email server. A /24 would be an embarrassment of riches for them.
Apple, HP and GE (IIRC) also have/had /8’s