He interviewed later that he would have lost his winter clothes, his glasses, and his contact lenses with the backpack. Not being able to see or read things would've been a pretty big obstacle for him, especially if he ended up with the Roadblocks in Rome or Wales.
I also actually like this season's Switzerland leg when compared with its nearly identical predecessor in Season 22. 22's had way too much train travel and not much substance in between. 24's had a few puzzling clues, a brain teaser at the auto museum, and no trains except for the beginning. (Plus a spectacular Pit Stop location)
I remember he also said that the bag was given to him by Dave & Rachel, and he didn't want to leave it behind, which I always thought was kinda silly, because DaveChel strike me as a team that would've definitely left it behind had it been the other way about.
But at least he clears up why he was so adamant about getting it back, if his glasses, etc, were in it.
I remember cussing that S22 Leg to hell with their trains, I still blame the trains for Chuck & Wynonas downfall.
Death by too many trains!
Edit - Finally got round to rewatching Leg 2, and it's actually a great Leg, despite Backpack Gate. It felt like everyone had equal screen time, and no one was invisible. Mark & Mall shooting out in front is fantastic, and their elimination is one of the most heartfelt there's ever been. It was a great send off with all the other teams there as well.
I'm still extremely upset over their elimination though.
They could've been 1st GODAMMIT!!!
I would have absolutely no problem with Mark & Bopper being asked back again.
The biggest WTF moment of the Leg was the Cowboys giving away the EP to CaroJen!
Guess they knew it would be burned, and not have to worry about it for the rest of the race.