I believe the reasoning is that web hosters were complaining for each IP it is charged
rather than per server.
So suppose you have 5 IPv4s, and you have 2 for shared clients, and then sold the other 3 as "dedicated IPs".
They claimed that you has to pay for all of those IPs
even if all of those are owned by the same WHM/Cpanel installation.
Other software like Cpanel/WHM and Softalicious don't do that and instead doesn't even use an IP or relies one a single IP as the "primary" one.