Red lantern is right. Basically, if the contract is non-guaranteed (or at least the last few years are), and you push your money back, and you get cut in a year or two, then you never get the money. And, as onerous as Romo's contract is, it is a possibility.
Also, pushing money back into later years hurts in another sense, even if it isn't a paycut. Lets say I offered you 100$ now, or $100 in 3 years. You would obviously take 100 now. Why wait 3 years for the same amount of money. I could even offer you 95$ now or $100 in 3 years, you'd probably still take the $95. Therefore $100 now is 'worth more' than $100 in 3 years. (also because you could invest that money, gain interest on it, etc, whereby it would be worth much more than $100 in 3 years)
I got a kick out of this. Only problem is you can't apply the logic to most of the NFL players that would blow that money instead of invest.