Who do you feel you're "showing" anything with a protest vote?

Protesting in the street works by showing the people in view that you're there in protest of a thing. However the viewer feels about you, the issue, or the concept of protesting, the fact that you're there doing it in that moment is public and undeniable. Protest votes, on the other hand, are a blip of mostly-invisible data that just get silently decoupled from the process and filed away once their irrelevance to the result is established. The election system, fucked and in need of reform as it is, has that built-in mechanism for quietly doing nothing in real life with your protest vote, and the system is certainly not going to be subverted or reformed at all by your having done it.

If that protest vote is the only means by which you're hoping to accomplish anything on Election Day, I'm still not sure I understand why one would bother.