Because of the dodgers protection, any spray(or rain) will find the back of the cockpit. With the boat heeled, the angled coamings and the seat deck form a open gutter to trap. water. The water travels to the widest part of that open gutter which is just into the bridgedeck. Instead of sitting in the puddle, these keep this area drained. That doesn't happen under sail too much but a heavy rain is drained off. More normal use is when sailing somebody knocks their drink over on the leeward side. Just sit up for a few seconds, it's gone. These keep the heavy water out of the locker drains which are above while heeled.

These scuppers are plumbed and tapped into fiberglass channels built into the fiberglass hull. Those hull channels are primarily designed to carry the deck water(which is often filled to the toe rails) away from two deck scuppers on each side.

I think this was typical wooden boat construction. Fiberglass made deep locker drains more effective eliminating a lot of this plumbing.

The best seat drain would be one that backs up to the coamings and with a deep enough drain to carry it onto the sole and out the lower drains. Probably what you have?