One point of view is that because it's low level API. Flexibility has been valuated over easy of use. In general I think that offering low level API is ~only ri

One point of view is that because it's low level API. Flexibility has been valuated over easy of use. In general I think that offering low level API is ~only right way to do for real application platform. You can always make more easier opinionated high level API over it (like three.js). If platform has only high level API you cannot make it another way around. Good example about this issue is CSS. I have a bit strong opinion about this but I really think that fact that we cannot polyfill flexbox / grid layouts is "proof" that this technology is not good enough and lower level API would be better option (and current CSS model maybe built on top of that).