I came up an academic philosopher, before I switched careers. When you're surrounded by academic philosophers, you become very used to argument as a default form of interaction. People expect that they'll be asked to give reasons for their assertions, and that those reasons will be scrutinized and challenged.
And it's great! You can learn a ton from having these arguments with smart, engaged interlocutors. It's not that ego doesn't come into it at all. Often, the "loser" of the argument -- and there isn't always one! -- won't admit they're wrong, and at some point will just bow out and live to fight another day. But the point is that everyone agrees they need reasons for their beliefs, and rebuttals to strong objections, and if they lack those they need to go find them. So the arguments serve to help you find those gaps. People argue because they want to be right, but being right is hard. So you work at it. You aren't just trying to assert dominance, you're trying to prove -- to yourself, first and foremost -- that you have the right beliefs! And if you can't, you might even change your mind.
Leaving that world was eye-opening, because I still expected people to feel a powerful need to justify their beliefs. But most people don't, and they take the mere act of asking for justification to be a personal attack. This cost me relationships with people until I really learned the lesson.