Its about building equity in your program.
A CBI appearance doesn't do anything for recruiting and program stature.
A bowl appearance and bowl win does build equity. Programs are largely judged by how many bowls they've been to and if they won them. It also extends the practice season by a month which helps with player development.
Only 4 teams in FBS make the playoff and there are only 10 conference championships to be won. For everyone else out there they are evaluated on their bowl performances. I would even argue the conference championships take a back seat to bowl games. The championship game is a relatively new development, prior to recently only die-hards could name who was the champion. Its not even clear unless you were following closely that OSU, Clemson and Alabama won their conference title games because they might not even need it for the playoff.
Going to a Bowl at 6-6, 7-5, is definately like going to the CBI. There are 35 Bowl Games, so 70 teams last year. There are only 130 FBS teams. So, over half of FBS gets a reward for not being very good.