The bowl is making money off the NIL of each of the players yeah they want to win the naty but they also don't want to adversely affect their earning potential the closer they get to earning a pro contract
the risk of career ending injury increases with the addition of each game... that is why they it seems like many will sit out not just because the bowls don't matter really but mostly my perception is they don't want to suffer a career ending or a combine limiting injury at the end of the season.
You want motivated players in the bowl games and playoffs make the $$$$$ reward for winning just playing worth it.