That is basically why the Standard Deduction exists.
True, and perhaps credible for a married couple with a 31k deduction, but the 15k deduction for an individual might be a bit rough for single folks.
It doesn’t really make a difference if both parents are working and make similar amounts. Then that part is no different from filing separately.
Point is a couple shares rent. A couple’s residence is unlikely to be twice the cost of a single residence, unless you have roommates. So 30k for a couple guess further than 15k living alone.