I think that's natural this is not only happen on ETH and LTC there is still a lot of altcoin who get the impact. But there are some coins when Bitcoin soar altcoin prices were also up it does not always happen depending on the market.
That's the true fact of altcoins having dependence over bitcoin. At present the value of bitcoin has gone down to $17500. Along with the decline of bitcoin most of the top altcoins with the market cap too has gone down. At some instances bitcoin used to soar when altcoins fall in price.