There is an inherent flaw in arguing that bitcoin is a speculative bubble, and does not have intrinsic value, without accepting that fiat money, as in national currencies, are also subject to this same criticism. If it wasn’t speculative and was backed by a physical asset, it would be impossible to keep it decentralised, which is the most exciting prospect with bitcoin or other cryptocurrencies. Such currencies are a new concept that defy definition by previous limitations imposed on currencies, their use may change as the technology and society does, but they are more than just a speculative asset.
Furthermore even with fiat currencies, there are no prices that are not somewhat speculative, with currency speculation being able to devalue or inflate a currency to a point at which a country’s stock market and overall economy can start to follow suit. This has been linked to financial crises, with fiat money being inflationary, fostering speculative bubbles itself and luring individuals, banks and states into traps of excessive debt. The speculative nature of fiat currency is most apparent in times of financial or political crisis, as when the currencies value or the authority underwriting it becomes questionable, people return to investing in or using precious metals, in this way gold really is the ultimate means of payment.
However crytocurrencies, despite being speculative and volatile (something that even applies to gold), are a unique digital asset and are formed from entries into the most secure database technology, so the comparison to fiat currency is not even a useful. Even security software is not as secure as blockchain systems, but bitcoin is built on a foundation of decentralised security, so provides a service that is fairer, more transparent and more secure than fiat currency. But cryptocurrencies are also new technology, they may require development as their usage increases, as with all technology, bitcoin requires adopting and incorporating to fully realise these benefits and function fully as a real currency.
As countries such as Sweden and China try to move towards being cashless societies and world tourism becomes ever popular, cryptocurrencies will offer more flexible monetary solutions and inevitably become more popular also. As country's currencies move away from paper and transition to the online world it is likely that transitions to cryptocurrencies will follow, becoming increasingly common either due to investment or trying to utilise the decentralised nature of the currencies to avoid international banking charges. But it's clear as a fundamentally different concept crytocurrencies may need this progress to occur first in order for societies to catch up with what the technology has to offer.