They were never there for every item--the publisherid field applies only to the publisher set in a custom version on a collection item (not just setting the versionid, which may have more than one publisher).
Because games and versions may have multiple publishers, this is the only time we can show publisherid.
A few years ago, they were there for every item. It may have been before the Versions started, but they absolutely were there. I remember, because that's how I would sync up my collection.
I did find another 3rd-party product that would get the info from the collection db to let me compare/contrast.
But, it definitely was there -- maybe 4-5 years ago, I guess...