Probably not very. It’s probably another vendor to pay to implement it. But many companies do this already.

In some places, this is basically the standard. In India, for example, it’s pretty much standard for that, especially in banking. My bank account there by default sends a text for basically anything. Every time there’s a transaction on my debit card, for example, I get an immediate text - it’s by default, and not even sure there’s an option to opt out if you wanted to.

that said, part of me is of the mind that 2FA is a lot of security theatre. The scam going around now is to have scammers get access to your cell phone number by switching it to a different carrier on a new SIM, then getting access to your bank account, etc. that way (when the 2FA code is sent there instead of to you). A good time to remind everyone to lock your phone number to your SIM/carrier, which locks it with a PIN which is an additional security step so random people can’t get port out your number off of your current SIM and deactivate it. If you want to Legitimately switch, you’ll have to provide the correct PIN as part of the porting process so that scammers can’t get access to your phone number.