1. Lethargy during a sideways market
2. Disregarding your strategy
3. Chasing somebody elses dream
4. Believing somebody elses FUD
5. Using money that you shouldnt be
6. Failing to properly do a self risk analysis before investing
If you can cope with these dangers then this type of investment will do well for you. This is a hands-off, long term method of investing. DYOR, find good coins with bright futures, buy and hold. Dont worry about the daily percentages
I think that the holder can be in two cases.
1. If a person truly believes in the coins that hold. The whole is a great option. For example, I believe in Bitcoin, so I hold it and accumulate it.
2. A person has a lot of money and doesn't want to engage in trade and trade education. He is satisfied with what he does, so he chooses a coin for holding himself (or listen someones advice) in order to sell it sometime (often he doesnt know when it will come 'Sometime').
In all other cases, the hold is unreasonable. You should be well versed in coins and trading. When money simply lies in coins and doesn't bring you a steady income, this is a luxury that is not permissible. In order to earn - you need to work.