> Right, it's hard to see what the advantage of debit would ever be.
Not being able to indebt yourself is THE major advantage of debit card. Not everybody in this world is reasonable when it is about spending and finance management.
In some European countries with a more conservative mindset related to debts (Germany, France, ...), people will tend to have the exact opposite stance :
"Why would I ever need a credit card ? It is dangerous. My debit card is accepted everywhere"