There's always been a vocal group who maintains that the IP addresses that are not visible on the internet should be returned. There are a number of problems with this argument.

Firstly, there are legitimate business reasons for having assigned, non-RFC1918 addresses that are only used internally. Interconnecting private networks belonging to different organizations that have overlapping 10.x addresses is a painful process. Sure it's possible to NAT, but given that the IP addresses are effectively an asset of the organization, why not use them? I'm not implying that this is right, but it's how the system was in the past and the cost of changing internal networking and applications could be very high.

Secondly, how do you prove that an IP address is accessible on the Internet? Many IPs do not respond to pings and I can easily set up a device that will answer for all IPs behind the corporate gateways.