Apple has done this kind of thing before. For example, they killed Flash, although that was no bad thing and there were open source alternatives such as HTML5 when they did that. I'd agree with the others that this was imposed on Presonus by Apple. It's probably uneconomical for them just to continue support for Windows otherwise they probably would have done.

Jeff Evans
It was an Apple thing not a Presonus thing.

That's bullcrap, and I'm certain you know it. So they had to rethink the approach on OSX? Sure. Why take away zero-latency monitoring from Windows users as well, though?
Their support absolutely stinks. I've had several major issues and setbacks with them over the years and have decided to not put any money towards their junk ever again.

Too late for me... I'm in up to me taters...