It’s an understandable move. Anyone that, for instance, wants to cheat the Fiverr system out of getting certain orders for free (Request something, and then when you get what you wanted, demand a refund) can’t cheat the system AS WELL AS get their money back.
So I understand it. The same way that if you return something to a store, many will give you store credit as opposed to a cash refund. It stops swindlers, so I don’t see how it’s greedy at all.
Also, you agreed to this when you signed up. These are the Terms of Service you agreed to follow:
Fiverr does not automatically refund payments made for cancelled orders back to your payment provider. Funds from order cancellations are refunded to the buyer’s balance as credit and are available for future purchases on Fiverr. Funds returned to your balance from cancelled orders will not include processing fees paid.