Showing off for your partner

What part of the male psyche is responsible for this behaviour? Does it ever stop? Even when your partner seems perfectly happy with you, warts and all. I'm pretty sure this is a specifically male trait.

I understand it when a man is in his 20s or 30s. There is probably some "mate-seeking" thing going on. I am now in my 70s, and I'm still trying to impress her. I like to think that she admires my muscles, (such as they are!), and my penis, ( such as it is!), and my overall physical prowess, ( such as it is!). I'm just an average guy, so a lot of this is obviously in my head 😄

I suspect that women, being much smarter, just accept this behaviour as "It's a guy thing....." Underneath all the outward confidence, there is still insecurity.

I also suspect that my partner is just happy that I make the effort to stay active and healthy. I doubt that she is too impressed with the rest of the performance.