A "standard" hireling you will only use 1 - 3 max (the max being yourself and 2 friends who each use 1) because you can't use more than one at once per person. The scaling is set to player > standard > gold. So 3 players + 3 standard hirelings is still going to be less than 6 players. Since you're able to use more than one at once, but they are just Hirelings still, the gold seal ones are less to reduce the likelyhood of you over-scaling yourself by accident. The secondary, and more obvious, reason is to make the Store ones a little more valuable.
Ok enough derailing...