It is not a valid question anymore than had you asked why don't you want to steal from people that work for a living and give it to people that spend all their money on drugs? Just because another has more toys than you, does not mean they cheated. Perhaps you are just lazy or not very smart.
The quesion should be why should we take even more money from the private sector and give it to the Government when doing so will not lower the debt or help the economy? It would make more sense to remove all deductions and lower all the rates. How much time and fraud would be saved if income was just income and you just send in your 10-15%? Exempt the first 50K ish for a person and $75K ish for a family if you want to protect the poor.