Why does he like putting himself down and making himself the butt of his jokes?

This guy I like is doing that and I don't understand why. Many of his jokes are about his screwups and he often puts himself down while he does that (not seriously, but somewhat jokingly). I just don't get it. Why would he do that? It's not like it makes him look good or anything, because I feel like he's lacking in self-confidence or something...and it's somewhat immature. Any ideas anyone? Thank you!
Why does he like putting himself down and making himself the butt of his jokes?
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