I used "value chain" euphemistically because you can get really complex on this and I wanted to spare the casual reader. I meant your credit card as an end-user product in your pocket and not meaning the card networks in isolation, but the value chain is roughly:

1. Merchant (bears little fraud risk but a lot of chargeback risk)

2. Payment Gateway (little direct risk but some liability risk)

3. Merchant Acquirer (more direct risk but mostly if merchants become insolvent)

4. Card Network (Visa/MC/AmEx - less risk but significant underlying costs managing a global technology that spans the financial system and needs to be distributed to almost every merchant of any scale in America)

5. Issuers (Banks + AmEx - most risk but get a big share of interchange fees)

I've surely missed something here that the very smart (and increasingly grumpy these days!) HN community will doubtlessly pile-on to correct, so I apologize in advance for errors or omissions... and I bow down if @patio11 swoops in to tell me about the complexity I've missed in either payments or Japanese economic/cultural conventions

Will also add that the benefit of credit is not overdraft but smoothing cash flow... if I'm living paycheck to paycheck and get paid every two weeks, I will incur essential expenses at the beginning of the fortnight that I can afford but lack cash in my account to pay now. I can't overdraft because I won't have the funds to deposit into that account for another two weeks. I'm getting a service that smooths my cashflow and there's a small premium added to reflect that. (Could you save up enough to avoid needing this? Is that a uniquely American way of living? I don't know! I'm making a descriptive claim not a normative one!)