I'll stop the discussion here because some regions do issue debit cards that are usable online like a credit card and are connected to Visa and Mastercard with 3DS and such, but other regions either treat that as a luxury item or requires you to pay a maintaining fee just like credit card (for Americans, yes in other countries even if you always paid in time there is still a separate maintenance fee) because they have local systems like Interac or iDeal that are operating indepedently.