The amount of friction I encounter every time I need to re-type my supposedly-"saved" credit card makes it painful to renew domains, and encourages me to switch to another registrar every time I need to do it.
Please truly save the credit card info and allow one-click checkouts. This is extremely common nowadays and there's no excuse not to provide it.
We're sorry to hear about this, but the reason we don't save the credit card numbers in the account is for your security. Say, by chance, your account gets hacked or the account is shared by more than one person...they can easily charge your card and create orders without your authorization. This way prevents such actions.
In any case, we appreciate your feedback and will forward it to the team.