In the US, credit cards convey many legal and financial protections not available otherwise, including built-in car insurance for rental cars, the ability to contest any payment and thereby receive a refund, and no liability for fraudulent purchases. As someone who pays the bill on time, using my no-fee rewards card for the last several years has also netted me more than $500 in free money.

Some nations give such protections to all their citizens regardless of payment form.

Here's an article from Get Rich Slowly which discusses the benefits of credit card use in more detail.

This program is presumably directed at countries where credit card use is already common. If you happen to use a credit card anyway (and this deal is available where you live), then switching to this is an essentially no-cost way of donating to SIAI (unless you have a rewards program on your card that's very good). If you don't live somewhere where credit cards are acceptable/viable, or if you don't have one personally, it probably isn't a good option for you.