Despite what people say, cryptocurrency still in the very early stage. This picture can put it into perspective.
Exchanges
At the moment, everyone is trading on exchanges like Poloniex, Bitterex, Bittrex,...
The problem with these exchanges is that they are centralized, they are controlled and ruled by governments.
We have heard news about people losing money because of exchanges close down or seized, BTC-e is a major example.
Also, what happens on these exchanges is that you don't actually own any of the coins in your wallet. They are just number displayed on your screen. The exchange owns them. That's why it is so fast to trade on these sites.
At the moment most exchanges use Bitcoin and Ethereum as the major currency for trading. The problem with this is that these coins are not built for trading.
Bitshares
This is the solution. Bitshares is an exchange but it is decentralized.
It is built solely for trading.
It is peer to peer so you will not lose your money when the FBI feels like they need some money so they close down exchange to steal our money.
Bitcoin is not king forever (maybe)
It is the father of all coins. However there are plenty of altcoins with features better suit to use as decentralized money. Bitcoin might well be king forever however, it there are any bugs or major problems, another altcoin will be on top.
A major example is the recent hard fork. Developers have realized one of the problem of BTC so they increased the size of the block. But if everyone in the world uses Bitcoin, they will need more size and more hard forks will happen like BBB, BBD, whatever...
BTC is used now to buy other coins. That is why its market volume is so high. But when people realize it is not built for trading, Bitshares will rule.