If membership in the community of Bitcoin holders has "value" to someone he/she is free to investment his/her entire savings into it. But he/she won't be able to benefit until a new member enters the community. And this is exactly how all fraudulent schemes operate. And that's why they all eventually collapse.
Money is something that doesn't require the addition of a new member to be able to provide benefit to its holder. That is because the benefit comes from the entitlement or utility that is behind money.
If the purpose of Bitcoin was that buyers "benefit" from it
simply by hodling it, then it has ponzi-like characteristics.
But that isn't the case. Bitcoin was designed as "peer to peer cash". The ultimate goal of those that follow Satoshi's original principles is that BTC eventually should enter a stable state, where there is no need for "new members" to enter the system, because it's not used for speculation but for trading goods and services, with an independent money circulation taking place in the Bitcoin ecosystem. In this scenario, the Bitcoin price should stay relatively stable.
And here we come to the question of "utility". If we reach the situation where the Bitcoin price is stable, how can people benefit from entering the Bitcoin ecosystem? Simply because it may have characteristics that are superior of other kinds of money. For example, you can simply send money from one country to another. You can get basic privacy (not a perfect one, but better than most non-crypto competitors). You don't depend from single private entities, like with PayPal and friends. And many people do already use Bitcoin to remove their dependancy of the government issued currency of a badly managed country like Venezuela. In the future, we can add that eventually it
may become one of the most accepted forms of money. We don't know, but isn't impossible.
