It's not about supporting weird hardware but about removing the unnecessary abstraction. E.g. in Vulkan you cannot directly write non-uniform inputs for the shaders because different GPUs may need that data in different formats and layouts. There is absolutely no reason to do this on a console, which only has one GPU and the layout of its data is very well known so you can just save a whole bunch of unnecessary code and gain an ability to use GPU compute to set up your draws on top of that.