I would genuinly like to know why a Jungler wouldn't smite a Baron just to be safe

The game was tough as it was, our top was feeding and seemed to like to just randomly go in 1v5. Our jungler didn't really like to fight for objectives, and the one that we should have had for free we lost (note that their jungler was dead) because he didn't feel the need to smite it.

I don't understand the thought process.