Its only more practical to treat zero more like a number. Do we ever say "I have infinity apples?" It makes sense to say that I have zero apples. Plus, we use infinity usually to see how something behaves (something like a series) as it approaches infinity. We even do the same thing...
I agree. Just accept the number. What did it ever do to you? In any system, like one with mathematical relations has to define what "something" is, on the contrary, it must also define what "nothing" is. Don't major in philosophy.