What is the usage of CYK algorithm in the real world considering we have algorithms with a much better Time complexity?
Here is one benefit:

Some grammars aren't LR(k).  Then it's useful to have CYK or some other form of GLR parsing.  GLR parsing is used in some compilers, where the most natural way to express the grammar leads to a grammar that isn't LR(k), or where ambiguities are resolved in a later pass (not part of the parser).