It's not like money because it's not scarce. I could generate karma easily by saying the right things on new posts, if I ever felt the urge to, which I never will because it's accreted anyway with no specific effort toward that goal. I've abandoned two other accounts to change my username and the reset to 0 karma didn't affect me one bit; I've never tried giving away all of my savings, but it would probably change my day-to-day life a lot.

Karma is a numeric representation of how people reacted to your post, including the votes by people who don't feel compelled to respond verbally--a substitute for the voting by attentive gazes or intentional ignoring that would serve the same purpose in meatspace. It's body language for the internet.