[hypertele-Xii]

Yeah, it's a high quality mouse. But the only excuse for this is it's slightly cheaper to make everything USB. PS/2 worked much better. It was limited to 200Hz but needed no polling. Motherboards just stopped providing the port.

[6510]

If the computer has to do anything at all it ads to complexity and it isn't doing other things. One could do something a bit like blue screening and add the mouse pointer to the video signal in the monitor. For basic functionality the computer only needs to know the x and y of clicks. (it could for laughs also report the colors in the area) Hover and other effects could be activated when [really] needed. As a bonus one could replace the hideous monitor configuration menus with a point and click interface.

[serendipitous]

This polling is not done by the CPU, this is a common misconception. In a typical modern system the only polling that happens with USB is done by the USB host controller and only when there is actual data the host controller generates interrupts for the CPU to process it. Obviously, when you configure the mouse at higher frequency you will get more interrupts and hence higher CPU usage but that has nothing to do with the polling.

[doublepg23]

Gaming or off the shelf prosumer mobos still have PS/2 on them occasionally. Although, it's probably just using a converter to USB anyway.