OK, question was about the role of bitcoin from the personal point of view. Somebody prefers to keep this asset, another is interesting in circulation, exchanging and spending.
Yes, because that's the point. No one gets to tell you what Bitcoin is "officially" for. If you think it's a currency, then go use it as a currency. If you think it's an investment, then go use it as an investment. Etc. Freedom at its best.
What does back bitcoin? It is more or less a game to consider that it is backed by demand. If new demand is "0" then the value of bitcoin may be "0" and it will be difficult to consider it as an investment or currency. If we imagine that all bitcoins are sold then new demand could appear only if bitcoin has been already treated as a currency, got its environment and law regulations (taxes, etc). Today fiat is used to buy bitcoin on the market, then bitcoin circularizes in buy/sell process, then it come out to be changed for fiat. Bitcoin seems to be a method. Method does no need to be baked. Method needs areas for implementation. Otherwise the method is useless. That is why the bitcoin´s implementation as a currency could keep it safe.