The simple answer is because of the little knowledge of trading. There are various types of trading, and not all of them are suitable for a person. Another reason is, that people come to start trading without learning it properly. Trading seems to be too easy, but they are not in reality.
People get trapped and lose a lot of money because they start doing binary trading and futures trading with a lot of leverage, which is more dangerous than gambling. They lose at the end and they get scared of trade because of that. Various platforms have trading options but not all of them are the same. People trade on CEX as well with Cross margin and they drain their entire account when they get liquidated.
That's what comes to their mind the first time they know the word trading, yes, they think that trading is an activity that can bring profits quickly, even though in reality it's not easy at all.
When they try to do it, what they think and what they feel will be very different. People like this are usually people who want an instant way to get money.
When they lose money, they will become afraid and will even think that trading is something like a Ponzi scheme or fraud. Even though it was their own fault.
People like this are people I meet a lot, and they even say something to invest in us so that we run their money (trade with their money) and share the profits.