I believe the reasoning was a simple tax grab. They saw the deduction as some sort of dodge allowing someone making $200,000 a year and paying $50,000 a year in

I believe the reasoning was a simple tax grab. They saw the deduction as some sort of dodge allowing someone making $200,000 a year and paying $50,000 a year in alimony, to move that $50k in income from a high tax brackets to a low brackets, even though now these are two separate people legally.