An almost constant criticism of Unity that I hear is that it's "too slow", that games made with it run slower than what their visuals would suggest. This has been such a common criticism of Unity for so long. So I don't think it's solely a response to requests from AAA studios either. My impression is that the current Unity model just doesn't scale by default (as in, yes it can be made to work but it's not the default and you'd be fighting with the architecture to do it). Or perhaps a much better way of saying it is that the default Unity architecture encourages less-experienced developers to write slower code. I've heard them say that "performance by default" is a goal for DOTS in a number of talks.