Nobody drops after the official slate of candidates has been established. Period. So stop speculating about what if X or Y dropped or why doesn't Z or K drop. It's not a thing we do. Learn the rules if you want to participate in this carnival.
Oh chill out zanas, it's a simple question (and, given that one left-wing minor candidate dropped out to endorse another candidate less than two months ago, a naturally occurring one). Hash answered it more than adequately. No need to get all high and mighty about it.