Strange things happen with coins.

I noticed that all coins have no value. No, of course they are worth something. BUT if blockchain is decentralization, out of government, state and dollars, why then the price depends on the dollar.
This can be seen on the graph of the STEEM coin. The coin is trading in bitcoins. But its real value is tied to the majority in this world to US dollars. Yesterday was a bit of bitcoin price. At the moment, the price grew by 10%, and then gradually due to the lack of demand and volumes, almost all lost. It is at this moment that the STEEM coin moves and moves, but exactly the opposite. In other words, the cost in US dollars has not changed. How much bitcoin has grown, has STEEM dropped so much. Please comment on the formation of the value of coins, regardless of bread, milk, meat and dollars.