That's just during the turbulent times. And that's because cashing out requires you to transfer your holdings into Bitcoin. Just like cashing in requires you to buy into Bitcoin.
Beware of the Bitcoin pump before the alt coin trade dump (moving of new Bitcoin, which is pumping the value temporarily into Bitcoin, out of Bitcoin and into alts). Although new money very well may HODL a portion in Bitcoin as a "reserve", similar to how you may hold Fiat in a trading account in reserve.
That's what... Bitcoin is the gateway to crypto world, we cannot enter or exit without it... No other coin in the near future can overtake it...If it goes down, whole market goes down.
You can also look at it as: When the rest of the market wants to cash out, it has to go through Bitcoin. So Bitcoin, in effect, is only as valuable as the rest of the market.
Meaning, Bitcoin is not the driver of the value of the crypto market, but merely the vehicle through which value transfers. As such, when the overall market corrects, the increase or decrease in the value of Bitcoin isn't the stimulus, but instead the change in value of Bitcoin is merely the response to the stimulus (i.e. market correction).
ETH can do it. I posted about it weeks ago and I believe it's happening now. But this is a turbulent transition just as any overthrow of a bad king has been throughout history.