Most users don't know what the words sms or totp mean. I'm not saying that totp isn't easy to implement in the grand scheme of things, but for many people it's not straight forward to setup. Entering a cellphone number and responding to text messages is well known since we've been doing it for 20 something years now.

I think totp would probably get more traction with normal users if people started calling it app verification, or something similar eventhough that is slightly incorrect.