It's a combination of (at least) two things, in my opinion. 1. Incorrect or incomplete understanding of the differences between CS and software engineering 2.

It's a combination of (at least) two things, in my opinion. 1. Incorrect or incomplete understanding of the differences between CS and software engineering 2. Ego and arrogance. There are plenty of very arrogant high achieving physics and engineering PhDs I know from my former life as an academic who would be ashamed at the arrogance of a lot of the folks in this field. In my view there is a very deep strain of "I know better than those who came before (and, incidentally, better than many now)." I've never seen anything quite like it in any other context.