Bitcoin is not sustainable as currency.

Unfortunately, bitcoin is not sustainable as currency.
Bitcoin is unlikely to replace current mining methods called pow (competitive mining methods) with steam mining methods such as POS (non-competitive mining methods) and has a fixed issue volume. Now, these shine advantages make it impossible to grow steadily with coins.
There is one post on Steam It today.
It's not that much attention, but it shows one of the reasons why Bitcoin's success can not be sustained.

Https://steemit.com/steem/@tamersameeh/11-3-miners-fees-on-a-bitcoin-transaction-this-is-crazy-steem-can-be-helpful

Cryto currency is more likely to be used for micro-payments or commerce that can not be accommodated in the bank system, rather than for the purpose of transmitting large amounts of money.
From this point of view, Bitcoin's transaction fees have already reached the level of disabling the function.
To enable micro-payments and to be used in commerce, the transaction fee should be zero, not close to zero.
Imagine what will happen to the transaction fee for bit coins in the future.

1. As the value of the beat coin increases, transaction fees increase.
2. As mining compensation decreases due to the half-life, the miners will try to raise transaction fees.
3. The cost of electric energy, which has a large share in the mining cost of the miners, will continue to increase. It is not likely to be imagined in capitalist society that new energy will be developed and reduce the cost of electricity.
4. As the bit coin value increases, the number of new participants participating in mining will increase.
5. Although there is a possibility of conflict between the user and the trader due to the increase in the commission fee, the number of the miners may be reduced due to the victory of the user. However, the security of the bit coin itself weakens .

As mentioned above, the bit coin is relatively low in the possibility of growing into coin due to the transaction fee (the original sin of the currency that issues a fixed amount by applying the half-life period) and the competitive mining method. Bitcoin is likely to remain a digital asset rather than functioning as a currency.
Crypto currency is not born as a digital asset, as its name implies. It was born to function in currency.
Suppose you ran a computer file and found somewhere 0.0001 bit coin (0.1$). Is it worth money?
The conclusion is worthless. This is because the 0.0001 bit coin can not be transferred by itself. The reason is that the transaction fee is higher than that.
The transaction fee reduces your money every time you make a transaction. Even if a person has a million-million-bit coin, if he repeatedly transfers from his wallet to his wallet hundred times a day, his bit coin balance converges to zero.
If you are expecting crypto currency to become the currency of the future, you have to think about transaction fee. With transaction fee crypto currency could not be sustainable currency.