Elephant in the Brain style model of signaling:
Actually showing that you have XYZ skill/trait is the most beneficial thing you can do, because others can verify you've got the goods and will hire your / like you / be on your team. So now there's an incentive for everyone to be constantly displaying there skills/traits. This takes up a lot of time and energy, and I'm gonna guess that anti-competition norms created "showing off" as a bad thing to do to prevent this "over saturation".
So if there's an "no showing-off" norm, what can you do? You signal (do non direct things to try and convey you have a skill or trait). It's still often that people signal all the time and it takes up time and energy, but it does seem a bit less wasteful than everyone "showing off" all the time.
Thanks on reminding me of nuance. Yeah, the "badly" does a lot of work, but also puts me in the right head space to guess at when I do and don't think real people would get annoyed at someone "showing off".
In light of reading through Raemon's shortform feed, I'm making my own. Here will be smaller ideas that are on my mind.