Title: Why not gray out/disable vote buttons on my own posts?

On Stack Overflow and other Stack Exchange sites, when I view one of my own posts, the upvote/downvote buttons are still clickable. If I click one, I get a message saying I can’t vote for my own post.

I wonder why the UI doesn’t simply gray out or disable those buttons instead. Graying them out seems simpler, clearer, and more professional than allowing the click and then showing a message.

Is there a design or technical reason for this behavior? I’m just curious why it works this way.

Sorry for the question; this always triggers my mind.