Shake is just amazingly fast. So even if its discontinued its still one of the the best tools around. Mainly its the no nonsense architecture of shake thats very appealing to many users. Shake reflects what you do much better. It does not hide stuff or take care of internals you don't want to be taken care of. Its much more like using the fusion custom node at all times without the time penalty.
However fusion is nicer to work on when speed or understanding is no issue.
Also theres a lot fo shake userbase thats highly, highly skilled.