Who tell you that altcoins are not bought for dollars. It seeing you have not been trade on coinbase and some other big exchange? Just the like eur and gpb move in direct proposion to usd is the same thing we are witnessing now because we are still new here and the market of altcoins is going to be behaving like that of bitcoin because the whole structure of blockchain technology and cryptocurrencies are build on bitcoin and that is the reason why altcoins seen not to be exchange directly with dollars.