Though the program has become widely popular, it's still very clearly a giveaway to the rich. Not only are the wealthy capable of saving a larger amount, we also allow their employers to contribute up to $56,000. Obviously, most employers are not going to contribute $56,000 to their employees retirement savings plan.
Up to 80% of the tax expenditure of 401k plans is captured by the top quintile of income earners. The plans amount to welfare for the wealthy, and indeed the government loses more revenue from these tax expenditures than it spends on many welfare programs like food stamps.