The key point is that if it’s not signed, it gives them an excuse to throw it away.
Do that to enough people and you end up with a big problem. The uncounted votes could swing the election, or you get a messy court case where some judges step in and basically decide the election on their own, or who knows what else.
At a minimum, it’s sets the stage for chaos. And from the chaos can emerge a chaotic outcome.
A bus pass maybe, that way you can just get on and not have to fumble around paying the fare when you board.