The marriage "Double Deduction" doesn't mean you get 2 deductions per person, rather each person receives the std deduction. (2 people, 2 deduction units for the claimant. The Income Tax form is performed as a couple, not as an individual.
Of course we can have it your way and insist single claimants only receive "Half" a deduction, but that doesn't make any more sense than somebody calling it a double deduction.
“2 people, 2 deduction units for the claimant. The Income Tax form is performed as a couple, not as an individual”
They get the deduction even if only one of them works and is issued a W2.
The rest of us subsidize that.