How does someone benefit?

If the taxpayers AZ taxable income puts them in the 4.5% tax bracket (3.5% surcharge tax plus the 1% income tax since the maximum tax rate is 4.5%), they may be able to take advantage of the 3.5% income tax rate on SBI income.

Since we are talking about it only helping those whose regular income tax bracket is over 3.5%.  but it isn't that "hard" to get into that tax bracket (MFJ with AZ taxable Income > $111,229 or other filing status > $55,615).  If they are already in the 4.17% or 4.5% bracket, then can choose to file the SBI and have their Schedule B, C, E, F (and some D) taxed at only 3.5%.

Whether this form solves a problem that does or does not exist is a political question.  However, the AZ legislation passed this law - and if we as tax professionals don't help our clients pay as little tax as they are legally required to pay - then we aren't doing our job.

Now, I would argue that Intuit also isn't doing their "job" in not even telling us when the form might be available (or specifically telling us that it will not if they choose not to do so).