If one entity owns the majority of Bitcoins, it doesn't necessarily mean others can't purchase Bitcoins. The entity owning the majority of Bitcoins can still choose to sell some of their holdings, allowing others to buy them. The concept of supply and demand would still apply, and as long as there are willing buyers and sellers, the market can continue to function.

The idea that owning 100% of a sound money tool like Bitcoin would be counterproductive is correct. If one entity were to own all the Bitcoins, there would be no one left to trade with, making the asset worthless to them. This is why it's unlikely that a single entity would be able to accumulate 100% of the Bitcoins, as it would go against their own incentives.

The fact that there are millions of HODLers, including many of us, who are willing to hold and provide demand for Bitcoins, makes it highly unlikely that a single entity could own all the Bitcoins. The existence of a large number of HODLers creates a decentralized and resilient market, where the risk of a single entity controlling all the Bitcoins is minimal.

It's also true that people who worry about this scenario often don't have custody of any Bitcoins themselves. By holding Bitcoins, individuals can contribute to the decentralization and security of the network, and alleviate concerns about a single entity controlling the majority of the assets.