What is the purpose of...?

I visit alot of blogs and some participate in this ritual of posting a picture and entitling the post Wordless Wednesday.  What is the purpose of Wordless Wednesday?   I guess what stumps me is that the title is Wordless Wednesday, but 9 times out of 10, there are comments that are included with the picure, so therefore it no longer is "Wordless...".  Yeah I know Google is my friend -----> off to Google "Wordless Wednesday".