Ego gets in the way of data. The hiring process is set up primarily to make the hiring party feel smart and powerful, so it's hard to break out of that and realize you don't really know much.
But it's incredible that it's so prevalent in tech, where people are supposedly so smart and data driven.
Not only ego. Other people too. Have you tried acting without ego? It might piss some people off, because it will expose them. Right in their smug faces. They will see how free you are and then look at themselves and become MAD.
Assuming you can act confident without ego. Most of the time you don't even have the social skills to put forth an opinion in a charismatic way. Weak voice, weak body language, stuttering, stumbling over your words, unsteady eye contact, failure to make people laugh and feel at ease. Bam, you lost. Made fool of youself. If you have no ego, you learn and carry on. It is difficult to do.
Acting with true humility rarely pisses anyone off.
Ego and insecurity are two separate things. You can mask insecurity with a big ego (and people often do that), but you can also be calm, confident and assertive sans ego if you're comfortable with yourself.
But it's incredible that it's so prevalent in tech, where people are supposedly so smart and data driven.