The price only alters because people panic sell altcoins as well when BTC price flinches. Altcoins are easier to mine, some are easier to gamble with, some can be traded fast, some keeps anonymity, some are secure. Those altcoins with a lot of balance and stability won't even budge with a small change in BTC value. However, the recent China's acts made some force sell all their online worth of cryptocurrencies. I guess that brought down the market price of several coins. There are a handful of coins like ARK, XMR and ETH which won't fail you.