It's absurd on the face of it. Nobody's gonna get me with any sob stories about how these guys are laying their livelihoods on the line and "easy for you to say, you're not the one risking career-ending injury." There is absolutely zero evidentiary support to suggest that playing in a bowl game has any significant risk to damaging a players NFL future.
It's a patently ludicrous argument. If you follow the "logic" through, then, yes, you HAVE to say these players should not play in the cream puff games AND any likely draft pick should immediately opt out of the rest of the season once it become apparent a team isn't making the playoffs. If midway through the season it's apparent that a team is on track for a 7-8 win type season and not making the playoffs and the team will only be going to a meaningless bowl game, then aren't the regular season games that would only qualify you for a meaningless bowl also meaningless games themselves? Why keep playing if the only goal is a meaningless bowl that you aren't going to play in anyway?
And, again, I come back to the cold, hard, irrefutable fact that suffering career-altering injuries in bowl games is a red herring argument. It's not a thing. It's such a negligible risk as to be non-existent.
Football carries inherent risks, including career-ending injuries. Every game played could be the last one. For NFL bound talent, playing in a bowl game could lead to the end of their career ($$$). So, in that aspect, I would disagree—a potential injury playing football is not a red herring. Ask Lattimore his opinion for context.
So, why does a player keep playing throughout the season if he could be hurt at any time? In today’s world, it most likely comes down to wanting exposure and stats. At some point (the end of the season) they must decide if it’s really necessary to continue showing how good they are (through sacks, catches, TD’s, yards, etc). By the time they reach the bowl game, they may have decided “enough is enough.”
IMO, playing in a bowl game comes down to character, as others have suggested. If a player gave his word (signed a scholarship), he should follow through and represent the university, including bowl games. After all, he’s receiving huge benefits in scholarships, room and board, medical, national exposure, etc.
But character doesn’t matter for a lot of players (and fans). It’s all about the money. I think many fans on here would argue pragmatically that if they were in the same situation, they’d opt out. It’s the unfortunate reality of money over character.