Ok fair enough your points are well taken and I appreciate your thoughtful reply. However, I don't think that the standard deduction exists for the reason you say it does. From the following link:
16th Amendment and Income Tax
Modern interpretation
In Commissioner v. Glenshaw Glass Co., 348 U.S. 426 (1955), the Supreme Court laid out what has become the modern understanding of what constitutes 'income' to which the Sixteenth Amendment applies, declaring that income taxes could be levied on "accessions to wealth, clearly realized, and over which the taxpayers have complete dominion." Under this definition, any increase in wealth - whether through wages, benefits, bonuses, sale of stock or other property at a profit, bets won, lucky finds, awards of punitive damages in a lawsuit, qui tam actions - are all within the definition of income, unless Congress makes a specific exemption (as it has for things like gifts, bequests, scholarships, and alimony).
Some lower courts have ruled that the Amendment authorized unapportioned direct taxes on income. However, the Supreme Court has always said that all income taxes are indirect.
Let's take a hypothetical but a fairly common situation. A person gets paid by an employer and receives a W-2 at the end of the year. That person commutes each day to his/her place of employment and incurs expenses for maintaining their employment. Clearly there are expenses that would not be incurred if that person was not working. The standard deduction is intended to in part cover those expenses. If we expand other necessary expenses to shelter, food and clothing (is there any argument that all people need these things?) then I think that a clear argument can be made that a certain level of income is needed just to purchase the necessities of life and that this income is not an "accession to wealth." Does the standard deduction cover all of these expenses? Of course not and this has been recognized by more than a few people. My understanding of this is the foundation of the Steve Forbes tax plan. Clearly there should be deductions for the basic necessities of life. Where to draw the line is debatable but it isn't at the level of the standard deduction for a family of 4 lets say.