I mean some will do it for the money. Id imagine if you are like a decent player along the lines of skill level from someone like a gade or cajunb in North for example, or GTR maybe, someone who simply will not be a part of a championship winning team. If someone like Astralis or FaZe offer you a role as a 6th, it could be very enticing. They'd be on high wages, and would more than likely have more time to spend with family, whilst still playing a few tournaments a year. Personally, I'd imagine 95% of players would obviously want to be playing full-time and would rather be on an inferior team to ensure that.
I feel like a 6 man roster is possibly viable, but only if the 6th player fully understands what is in store for them and accepts that. I feel that Bubxkji was brought in at the wrong time, when es3tag started to really perform and when Xyp came back. He has been rotting on the bench since he left Mad lions, which is really unfortunate as he's a serious talent and he was a very exciting player to watch. He may have been blinded by the money and prestige of playing for Astralis, not fully understanding what implications that could have for his career. I do believe that gla1ve may be benched soon though and that Bubzkji will have his chance. If gla1ve isn't the IGL anymore then what is the point of keeping him on the team?