Because I am interested in technological advances, because I enjoy to play with random things and see what runs on what. I've run every compatible OS on all of my Pi's to test and mess around with. I didn't have a use for the Pi3, but now I have, and I can test to see if windows runs fine on one, if it does, that makes a whole world of difference, and windows on a small portable device has so many advantages in terms of ease of use.
I think you read the headline then posted.
“Previously, Windows IoT Core was the only Windows operating system available on Raspberry Pi devices. This new package offers functionality similar to the standard desktop version of Windows 10.”