All systems use numbers to express the quantity of shares in a system that someone bought. But in the bitcoin system these shares are worthless because their holders are unable to return their investments from the system that issued them.
I am still not sure whether you truly don't understand or if you are just pretending. Bitcoin is not a system of "shares" like in traditional stock markets. Why do you keep comparing them?
To put it simply, Bitcoin is merely a method of transferring value between two parties. P2P type of payment system. There is no issuer of shares or company in which you invested funds when you exchange fiat currency for cryptocurrency. You simply exchanged one currency for another while, at the same time, someone else did the same in the opposite direction. That is it!