Some of the reasons why Cryptocurrencies might disappear are:
1. High transactions costs, preventing small-scale transactions or even micro/nano transactions required for the Internet of Things.
2. Low number of transactions per second, which prevents it from being used in everyday life.
3. A centralised cryptocurrency that can be controlled by a few mining pools, if they wanted to.
4. An unsustainable energy consumption, even if all miners would switch to clean energy.
1. High transactions costs, preventing small-scale transactions or even micro/nano transactions required for the Internet of Things.
2. Low number of transactions per second, which prevents it from being used in everyday life.
3. A centralised cryptocurrency that can be controlled by a few mining pools, if they wanted to.
4. An unsustainable energy consumption, even if all miners would switch to clean energy.
You have not listed the no.1 reason (that is the one given by the OP). The single biggest threat to the existence of cryptocurrency comes from the government. Being a resident of India, I know how difficult it can get if the government starts harassing the cryptocurrency users. Last year, around 100,000 individuals received notices from the income tax department as the government closed down the local exchanges and retrieved the user data from them. Banks closed down any savings account that was even remotely linked to crypto-trading and as a result most of the trading has either gone underground or has shifted to P2P.
