I ask out of morbid curiosity. Took a look under the hood of the Microsoft by the Numbers [1] microsite and noticed the captivating background gradient was actually an image [2] not CSS gradient.<p>I can guess a few reasons<p>* Consistent color reproduction on all devices<p>* Some gradients are difficult to reproduce and may require multiple layers<p>* Presentation matters more than performance and the code has a one off use<p>[1] https://news.microsoft.com/bythenumbers/en/homepage<p>[2] https://news.microsoft.com/bythenumbers/assets/uploads/00/bg-2048.jpg