Optional Means Optional!!
I'm including the snippet below directly from Tuck's Insider's Guide to the Tuck Essays because every school feels the same about Optional essays or anything else labeled "Optional" anywhere in the application. (Emphasis mine) The fact that they even wrote this so plainly is strong evidence that their level of annoyance is extremely high regarding this issue, so ignore these guidelines at your own risk. More is not necessarily better, and you can actually distinguish yourself by showing the confidence to write less! Here it is:
"3) (Optional) Please provide any additional insight or information that you have not addressed elsewhere that may be helpful in reviewing your application (e.g., unusual choice of evaluators, weaknesses in academic performance, unexplained job gaps or changes, etc.). Complete this question only if you feel your candidacy is not fully represented by this application.
Optional is optional! We are NOT docking you for an empty optional essay. Actually, quite the opposite; if you give us an extra five paragraphs to read and it’s not necessary, we will question your judgment or your ability to express yourself succinctly elsewhere. For example, you do not need to further declare your love for Tuck here when you can articulate that in the first essay and the interview.