Consider like this. Leverage on the way up -> take profits in BTC at the top -> altcoins drop harder to unwind massive moves -> value deposits into BTC -> then fiat.
BTC is still money but doesn't work well as cash. But huge volumes of BTC are available on exchanges for traders to borrow to leverage with. I think this gives BTC its value
2/2 would protect BCH during bear cycles as traders unwind positions where BCH was in denominator. Unwinding a trade would require buying BCH and selling the altcoin
1/2 You’d have to use BCH as cash to have a trading pair with it like on Poloniex. I suspect altcoin trading makes up >75% of BTCs use. Having BCH as a denomination would protect