Because they don't want the workers voting.
If you "can't go to the ballot because you need to work" you are a plebeian, and so they have a way of excluding you while technically not excluding you.
A lot of modern oligarchy is powered by these technicalities. Technically everyone has a "right to" participate in the system, but the whole apparatus is rigged in such a way that in material reality only the same nobility caste that has called the shots since the bronze fucking age gets to call the shots.