well, on this board, I have seen people talk about how "meaningless" most bowl games are outside of the playoff games or the major Jan 1st games.
so, in that sense, if a player decides not to participate, that player apparently sees the game as 'meaningless' also. I guess the big issue is risk of injury. whatever the odds are, the idea that Player X could blow out his knee in the Who-Ha Bowl, and go from a 2nd round pick to undrafted, is a risk that some are not willing to take.
and by going into the pre-combine workout program, they see a chance to enhance their draft status.
what this does for me is shift the calendar. Instead of the Bowl Game being the end of the season, it really becomes the start of the next season as younger players and backups get a chance to show what they can do. and that's fine.