Credits. Why? Why? Why?

I've been a long time client (since early days of Dolphin). My biggest complaint is 'Credits'. A platform that forces users to overpay for every app. At the very least, why can't we purchase an exact amount of credits?

I was going to purchase an app but the 'Credits' program made me decide to pass. I would have to pay TWENTY dollars over the cost of the app. I will never use that overpayment for anything else.

Why can't we have the option of paying with credits, PayPal or credit card?