I know a large number of developers that have only used Eclipse, and swear by it. The prime motivation for using it seems to be that it's free.

I hired a couple of them for a gig a while ago, and gave them IDEA licenses so we'd all be running in the same IDE. They were instant converts.

I think the results are reflecting the larger numbers of developers who adopt the best free IDE rather than pay money for one. Might be safe to say it's more of a "what IDE are you using" vs. "best IDE".