Perhaps this is a naive way of looking at it, but from someone who just barely grasps Bitcoin, it seems like a place for rich people to park money.
Well, you don't have money to park it indefinitely, at some point you want to spend it, otherwise you could just set it on fire and not worry about parking it somewhere to begin with. So the selling part is non-optional.
> the selling part is non-optional
That is not true.
Bitcoin is best thought of as a block of real-estate on a virtual Manhattan. Some of the wealthiest families in (IRL) Manhattan are wealthy because they've owned a block of land on Manhattan for generations and have never sold. They borrow against their asset to live and the asset keeps appreciating. Bitcoin will be, and already is, no different. There are people that do this exact thing with Bitcoin.