Why not? I’ll happily dictate my credit card number into my phone, heck I’ll throw open my apartment window and loudly yell my credit card number into the street, along with the expiration and CVV2, with zero fear that someone or something will actually be listening and recording it / writing it down.

By contrast I refuse to send my credit card number in an email or post it on a non-SSL site.

Guess which way I’ve only ever had my credit card number stolen?