Not OP, but I think I can add my 2c here.

It means (pun intended) that the meaning is not self sustaining term in our reality - there is no absolute meaning outside of our perception. There is only relative meaning (as in what kind of meaning my perception assigns to things that can be observed by me - simply put - we create our own meaning).

It can be simplified further to there is no meaning or the meaning does not exist but in my opinion this is oversimplification and reeks of nihilism.

So if You look at things from the point of view described above the "why" question (which can be paraphrased to "what is the meaning") is wrong.