The U. S. Postal Service, state motor vehicle departments and other government agencies also have the taxing power of government to get money and therefore are less diligent about pleasing customers. You can bet the rent money that if Wal-Mart and other businesses had the power to take our money by force, they would be less interested and willing to please us.
The big difference between entities that serve us well and those who do not lies in what motivates them. Wal-Mart and millions of other businesses are profit-motivated whereas government schools, USPS and state motor vehicle departments are not.
In the market, when a firm fails to please its customers and fails to earn a profit, it goes bankrupt, making those resources available to another that might do better. That's unless government steps in to bail it out. Bailouts send the message to continue doing a poor job of pleasing customers and husbanding resources. Government-owned nonprofit entities are immune to the ruthless market discipline of being forced to please customers. The same can be said of businesses that receive government subsidies.
The ruthlessness of the market discipline, which forces firms to please customers and thereby earn profits, goes a long way toward explaining hostility toward free market capitalism.