Most people hold their coins in centralized exchanges, if the exchanges got hacked, failure or bankrupt, the customers high likely lost their money.

Non custodial wallet users will back up their seed phrase on somewhere else, if someone can access the seed phrase, their will lost all of their money. Or if the owner forget with the back up, they will lost  the coins.

If you buy, sell and hold Bitcoin on the countries where Bitcoin get banned, your coins could be confiscated and you will get jailed.

If you didn't report and paid the capital gain tax you made from Bitcoin, you could be investigated, got penalty fees and risk of going to jail for committing tax evasion.