“Sideways” means low volatility; the extreme of sideways-ness is price stability.
The theoretically ideal form of money is price-stable. Volatility only benefits traders, at the expense of everyone else.
If BTC could become price-stable,* then I would prefer that. The world cannot run on volatile money alone, nor on deflationary money alone. (Note to Jay: I am perfectly well aware that price-stable BTC will never happen.)
Since I don’t swing-trade, the only thing uncomfortable to me about a sideways market is that I never know whether it’s about to crash, or about to moon.
* I mean price-stable according to an index of goods and services. That means rising against the dollar, as the dollar depreciates from inflation. The dollar is not price-stable; to the contrary, the dollar is a volatile currency. Have you seen dollar prices lately!? Not only the obvious increase in prices, but the fluctuations as markets adapt to price shocks.
What if Goods and Services get priced in Bitcoin one day? We already saw people in failed economies like venezuela abandon their currencies for something harder like the dollar. What if we see this happening on a bigger scale with Bitcoin, because fiat will become so worthless that no one wants to use it anymore, similar to the bolivar. Bitcoin will atleast increase the pressure on fiat to not let get things out of hand that much.