We require the phone number for security purposes. A code can be sent to a phone number instead of using a password, and it can also act as 2 factor authentication. 

If you would prefer to use an Authenticator app, you can go to https://accounts.intuit.com and set one up in the Sign in & security section.

My concern is manditory requirement for a phone number, which I don't want, consider phone obsolete when there is free text, voice, and video connections available with an internet connection and the requirement has nothing to do with security since there are alternative apps available.

To me it seems like another hidden cost for your product, forcing me to purchase something I don't need and have to ask other people to handle the phone number requirement for me.

I see it as either a marketing gimmick, or worse still your company acting as an agent for the phone companies.

Sorry for the venting but not all can afford an optional (not manditory) cell phone and just helps keep the protected cell phone industry prices high!