Anyone tracking signup conversion will realize that phone numbers are autofilled whereas 2FA requires an installation for a greater number of users, leading to drop-off.
2FA apps also require me to do many more actions as opposed to SMS as notification. Would be much better if there was some sort of nudge mechanism for phone to display the proper code.
Microsoft does this. eBay also. And steam. Once you install the app, any time there is a sign in, you get a pop up on your phone. Yes/no button. Very convenient.