Need for audiophile switch if using ethernet optical??

To keep noise out.

But optical eliminates noise. So why worry about a noisy switch that precedes optical ethernet?

What are you trying to switch? 2 optical sources? 

You did not specify before or after so it is a dumb question. The egg or the road crossing?
Why is the chicken?

Are you actually trying to accomplish anything useful?

Actually the short answer is for switching, i.e. multiplexed outputs.