In short, Bitcoin isn't for everybody. The problem is that there are so many people who jump right into it without doing a quick due diligence. Especially during a bull run when Bitcoin is all over the news highlighting its price increase, many start buying without understanding anything.
One thing you're missing, however, is the responsibility that accompanies a Bitcoin investment. To invest in Bitcoin is to be your own bank. That requires you to at least understand how keeping Bitcoin is properly done. If you don't want to spend time and effort understanding wallets and private keys and whatnot, Bitcoin is also not for you.
People are greedy in nature, so when they witnessed how profitable bitcoin is, they rushed into a decision where they will come to regret in the end. So it’s not surprising to see a lot of investors rush to buy and sell, and end up at loss. They invested into bitcoin blindly, without knowing first when is the best entry and exit in order to maximize the possible outcome. As a result, they all suffer from losses, while others have cursed bitcoin and call it as a Ponzi scheme.