1. Credit cards are not that common. People usually have debit cards. Those can sometimes be used online but they're not widely accepted. My debit card is Maestro, which is not accepted in many places.

2. Even with my Mastercard credit card, the process is still inconvenient. For small purchases, it's fine. But for larger ones, there is an annoying second factor authentication, I have to enter a special password, and the wait to receive an SMS.

3. Visa and Mastercard fees. Most of the time these are paid by the merchant. But sometimes the customer has to pay more if the payment method is credit card. Some places don't accept these at all.

In general iDEAL is simple, secure and convenient. Not only to pay online, but also for example for splitting a bill with friends. I'm very happy to see this being adopted more widely in Europe.