They won't give you credit because you have no credit history and they see that as a risk. It's a real catch 22, I had the same problem. I have one credit card that I was able to get on my own through my bank, but I still have trouble getting credit elsewhere. Buying a car in your own name would be a great way to establish some credit, but it'll most likely be a lot more expensive.
I was able to move into my first apartment on my own without a co-signer, yet I recently got denied for a fucking Victoria's Secret credit card, go figure.