I think a lot of the reasons I am the way that I am is because I'm hyper aware of how I might come across, and I'd hate to come across as something/someone that annoys me. Being somewhat humble is a positive product of that, although there are a lot of downsides too.
I have an inner monologue that sounds strikingly similar to something off Animal Planet.
I don't think they try to be humble, it's that being humble takes less energy than not being humble. Just takes too much effort to show everyone how awesome they are
I dated an ISTP a few years ago. He played poker professionally and was far removed from being humble about it. He didn't mind taking the energy to show just how awesome he was at it because that's how he paid his bills.
"How dreadful!" cried Lord Henry. "I can stand brute force, but brute reason is quite unbearable. There is something unfair about its use. It is hitting below the intellect." ~ Oscar Wilde - The picture of Dorian Gray