First you have to figure out how to use the webpage / app to get the virtual credit card number. Once you know, you still have to log into a separate service and click a few buttons. With PayPal or Amazon Payments you just click your password manager's button to log you in right in the checkout process on the same webpage.
Some banks will issue one-time use numbers for your cards, limited to a certain transaction amount and then they're gone. A pretty cool idea, but until they have an app that generates these numbers at the push of a button nobody really uses them. Too much of a hassle.
