Bitcoin is a scarce currency and has a fixed supply volume of 21 million. Therefore, cryptocurrencies will remain the means of speculation and nothing more, until a better economical breakthrough occurs.
Your post makes no sense at all, what does fixed supply has to do with speculation? And do you know that a lot of coins are inflationary, and they are still more speculative than Bitcoin. And what economic breakthrough are you talking about?
Bitcoin is speculative because it's not widely adopted, and there's a lot of uncertainty about how much adoption it will get. Bitcoin's supply is irrelevant to its adoption.