You send me $900 and I will give you a piece of paper, not a cert, telling you that you have 100 shares of Ford Motor Company.
What is a check? For that matter what is a twenty dollar bill? It's all nothing more than a promise of value. What is any stock certificate? It's all merely a representation of value. Unless you're now suggesting a barter system, I think you had better get used to those pieces of paper.