Some people say that investing in bitcoin is not really an investment, since it does not create any value
Correct. Money has no direct use value. Having more or less makes no difference. Saving money is just saving. Investment is when the saver buys capital goods with the intention to produce something.
But note: Somebody must save before investing is possible. Saving has to come first.
And: On the individual level there is no difference, because it is easy to transform money to capital and back.
In modern economics theory, value is only decided by supply and demand. If investing in bitcoin can satisfy people's certain kind of demand, then it creates value
Investing in bitcoin, is to inject capital into the bitcoin currency system. It will support and raise the bitcoin exchange rates. While the exchange rate continuously improve, it will gain popularity and credibility, thus satisfy the demand of an anti-inflation medium of saving
Saving/hoarding/speculating in bitcoin raises the value of the bitcoin unit to a level higher than the current value would be, if only the current usage was taken into account. Without speculation, the current value could be less than a dollar.
Stated otherwise: If the coin was constructed such that the volume of coins increased with usage, speculation would be futile and the value based on use in indirect exchange could be less than a dollar per coin.
This demand can not be satisfied by ever-inflating fiat money, people can only put their excessive funds into stock/ real estate / gold, but these assets are risky and difficult to transfer
And satisfying this demand will enhance the economy activity of the whole society, after people had some savings that do not lose its value over time, they will have the confidence to spend
Correct. Sound money makes saving in money possible, possibly reducing production of things that people don't really want, but have to buy because of inflation.
Like any other investment, the investment in bitcoin also has risk. But due to limited supply of coins, that risk is much lower than any other investment vehicles, it has a reward/risk ratio of over 30:1
Absolutely correct. Just get in if you are not in already.