Why do corporate Uncles forget they have five & kids if a woman employee is nice to them ?

I have seen this time and time again, corp dudes/uncles have wife and kids yet when a female employee is idk treats them normally nice given the corporate culture they forget the line between supervising them to straight up flirting with them, the incidents are insane - why do they get so pervy. I once saw a man with child in his hand and his wife sitting beside him on a metro, she was looking elsewhere and this dude was creepily looking at me, I could never forget the disgust I felt