Earnings by Segment is a Sulvo method of showing greater visibility into various buyer segments and their total weight in terms of total advertiser spend
By observing all buyer segments in detail it is possible to examine earnings on each ad unit much more granularly. This way, it is visible which segment is bringing the most value to the site. A single CPM value generally does not show enough granularity to do meaningful pricing analysis, hence regular CPM as an aggregate value is typically not used anymore at the biggest media companies.