The federal government and Apple computer do not make for a very interesting comparison. Apple is a publicly traded corporation whose management seeks to maximize profit, while the United States is a democratic republic.
Apple engages in profitable business lines, eliminating them if they prove not to be. Our national highway system is not itself profitable. It requires a massive, ongoing capital investment, yet served as an important factor in post-World War II growth in the United States. The (forced) taxable contributions that fueled and continue to support this network are important may be abhorrent to some, but their collection by a state overcomes the significant barriers to entry a national highway system entails for the private sector. A private highway system would incur addition transaction costs, such as a potentially inconvenient array of toll collections for one, than a federally-funded system. Indeed, all roads may lead to Wal-Mart under a private system; a state-run and taxpayer financed system balances coercive revenue collection with correcting an (arguable) area of market failure.
In short, the federal government’s purpose is not profit maximization. Though there are many systemic problems with our system which make for fodder for this website, the Treasury’s comparison to a corporation is not very interesting.