I recently watched a video of fitness youtuber talking about him testing his 1RM frequently (about every 6-8 weeks), which would replace one of his "regular" training days. He does that by calculating his 1RM and then trying to lift that with some friends spotting him. Unfortunatly he does not talk why he does that. I won't include the video because it is not in english and doesn't really contribute to the question itself other than giving the context of why I'm asking the question in the first place.
When training in a bodybuilding-like fashion (training for hyportrophy and gaining muscle size), should one test their 1RM frequently? If yes, why? What are the benefits of that (except maybe boosting your ego)?