The network grows more easily and more widespread under a 3-degree setup. Even when your direct referrals does not trade much, you can still earn generous commission.
With a 3-degree setup, affiliate can achieve targeted trade volumes much faster and earn much more commission.
Walk through the huge difference by data
For example, if A invited 10 people as direct referrals, these 10 people each invited 10 people as their direct referrals. According to a 2-degree affiliate setup, A has 10 direct referrals, 100 2nd degree referrals. But if those 100 2nd-degree referrals each invites 10 people again.
According to the 3-degree affiliate setup, A would have 1000 3nd-degree referrals!
Let's say each people generate 1 BTC trade fee.
earning = 30% * 10 + 30% * 30% * 100 = 12 BTC
earning = 30% * 10 + 30% * 30% * 100 + 30% * 30% * 30% * 1000 = 12 BTC + 27 BTC = 39 BTC