Why? These aren't automatically available in nature.It turns out the answer to your question doesn't require empathy for your fellow man to understand. (Of course, if we were assuming this, the answer to the question would be largely obvious.)
A lot of things aren't automatically available in nature. Police, the military, public schools, and your broadband connection all come to mind.
It turns out that governments and society work based on this concept you may have heard of called a "social contract." Look it up. Saying there's a "master-slave" relationship implied by citizens deserving to have their basic needs met is either really ignorant or very disingenuous. Every citizen of this country is part of the contract, whether you realize it or not.
If you allow a large enough part of the society to become a desperate underclass, you'll find that they'll become dangerous to the rest of the society. Dealing with these problems will cost you more in taxes than simply improving infrastructure at large as a preventative measure.
Or, put more bluntly: the safety of the rich and upper middle class isn't automatically guaranteed in nature either. If you really want to take the nihilist approach you imply, then you'll find that poor people won't just walk idly by your house in despair; they'll just kill you and take your money. Or they'll get so sick that you have no choice but to start paying for their health care lest you catch the plague. In "nature" no one cares how well you code, only how well you can fend for yourself in the wild. Is that really the society you want?