I wonder if it has anything to do with the fact that the data is actually owned by LinkedIn users, and they expressed that they want their data to be publicly available?
Unlikely. The license to LinkedIn retains ownership, but the user's retention of information ownership doesn't compel LinkedIn to affirmatively do things with that data (i.e. LinkedIn isn't forced to vend the data to a given consumer if the user says so).
The license further goes on to clarify that LinkedIn will vend public data to search engines, but the definition of "search engine" is almost certainly assumed (by LinkedIn, at least) to be up to them.
The license further goes on to clarify that LinkedIn will vend public data to search engines, but the definition of "search engine" is almost certainly assumed (by LinkedIn, at least) to be up to them.