There is.

The main problem with altcoins is that there is next to no solid depth in any of their fiat orderbooks. If an altcoin whale for example is trying to liquidate its holdings for the best possible price (without suffering from too much slippage), they'll have to carefully dump their own orderbook down, but also convert a large chunk of their altcoins to Bitcoin from where these Bitcoins will be sold for USD.

If you look at how altcoins have been bleeding lately, and especially Ethereum, then it's safe to say that Ethereum is one of the main reasons there is so much selling pressure.

Market cap of both Bitcoin and Ethereum in Juli of this year;

Bitcoin $126 billion.
Ethereum $50.5 billion.

Market cap of both Bitcoin and Ethereum today;

Bitcoin $120 billion. -5%
Ethereum $25 billion. -50%

Ethereum is just one pile of shit. ICO's need cold hard fiat, no shitty token that's worth $500 one day and $250 the other day.