Don't give me any religious reasons as that's just a coping mechanism.
But it is the human mind that seeks meaning in everything. The fish are not looking for it, neither are the birds. They are participating in a huge dance of atoms and molecules, attuned to a much higher system than the limited human mind can comprehend. If you continue to seek a rational meaning behind life, you won’t find one, because the mind is not the vehicle through which this kind of meaning is comprehended.
It’s like looking at an atom through a high-powered microscope. It will elude you because the very act of observation alters the atom (the light of the scanning electron microscope interacts with the atomic structure). This applies to the meaning of life too.
Don’t expect your thinking apparatus to come up with some kind of meaning. But if you allow yourself to understand other forms of perception, you will find it.