Because a text message is not a second factor worth having. A phone number can be moved to somebody else's SIM with a phone call to the network, and it has been, repeatedly, to people who thought a code by text was protecting them.
It would also mean an account with a messaging service, a per-message cost, and your customers' phone numbers going to a third party. An authenticator app costs nothing, works on a plane, and sends nothing anywhere.
Still stuck? Ask the developers who wrote it. We aim to reply within one business day.
Login Security
Stop the machines guessing at your passwords, and see exactly who has been trying.
From $19 a year · every feature · 30-day refund
