Why did people start qualifying statements with the word "arguably"?

I had always heard it as “unarguably.”

The first time I heard it it was from my daughter several years ago. We had the family over for dinner and my daughter said,“Rick arguably makes the best fried chicken ever!”

Reading an article on Stone’s indictment, there was a sideline that read, “Judge delays sentencing Flynn after rebuke: ‘Arguably, you sold your country out!’ ”

Isn’t that redundant? I mean, you can argue ANYTHING so why stick that word in? It also seems to weaken the person’s position.