Why does ordering Raspberry Pi require credit cards?

How come companies don't accept Cash, check, money order?
Cash, check, and money order works for Banks.

How come most of websites accept master card, paypal, visa, etc?

Do they want to violate people's privacy by showing numbers online?
Shouldn't these people worry about spyware, cookieware, etc?

Laziness. Impatience.

Checks:
They won't ship until they receive the check and verify it won't bounce.
Someone on the Accounts Receivable team has to either make a run to the bank or they have to mail the checks the bank. Check Fraud used to be a much greater concern than it is now. Even so, it is still a problem.

Money Orders:
See bank runs and postal deposits mentioned before.

No business accepts cash in the mail. It is ill advised. They will not ship until they receive payment. Cash will seldom arrive where it is intended.

Credit and Paypal are electronic and relatively instant.

Buy a prepaid credit card most sites will accept them call Customer Service to verify they can accept them before getting the card.

So you are asking why companies online only accept electronic forms of payment rather than physical cash or pieces of paper?

Isn't the answer obvious?

Even PayPal isn't necessarily that trouble free. An organization I work with uses PayPal for online transactions. Some of those transactions--but very few of them--PayPal handles as "electronic checks". One of them this year bounced...the payers bank refused the e-check. The person that tendered it has been notified...someone is going to have to pony up cash to pick up a convention badge....

I'd look through the OP's post history and then make the decision as to if he's a troll or not....