Children have the remarkable ability to see the world as it truly is, and so are able to ask the most profound questions. As adults, we learn to obfuscate our, ah, knowledge deficiencies in various ways, and so lose that ability over time. I'm of the opinion that great physicists are like children in being able to see through to the heart of the matter, and ask -- and answer -- questions that matter. This is certainly a theme you can see with Einstein, Bohr, Feynman, and others.
Why do I say this? Because GP's question was profound, and saying "it's because charge comes from spin" is the sort of obfuscatory answer I see most physicists give very, very often when they're faced with such questions.
That's completely aside from the fact that "it's because charge comes from spin" is entirely incorrect. All charged particles have spin, but not all particles with the same spin and other similar properties are charged.
