The government is not a charity and it should not be treated as such. The Left has a tendency to use the government as a means of doing charitable works. Hence, they want to raise taxes on the rich and give the money to the poor, kind of like Robin Hood. Basically, it’s forced sharing or forced charity.
Putting aside the discussion of whether putting a gun to the head of a rich man to make him share is morally acceptable or not, I’d like to point out the problem of the effectiveness of government charity. I had a reference but I lost it, so I can’t give you the specific link. It comes from debatewise.org. Anyway, the claim is that 30% of the money given to the government for a charitable program will find its way into the hands of the poor. The average charity, however, has a return of 65% – 75% and sometimes as much as 90% or more. From that, assuming it’s true (which you really can’t because I lost the link) the case is heavily weighted in favor of the private charities.
The biggest advantage of private charities, though, is that they allow you to pick and choose and prioritize according to your own desire. A worthy charity for me may not be a worthy charity for you and vice versa. There are over 300 million people in this country, all unique with different views on what needs to be fixed or what needs support. Trying a one-size-fits-all approach with all the money of the taxpayers fails to recognize the value of an individual’s own assessments. I can decide what institutions and organizations I wish to support; I don’t need government to make that decision for me. Relying on private charities preserves freedom and diminishes the government’s reach and power. All in all, a good thing.