People are willing to lose a small but predictable amount of money to avoid occasionally and unpredictably losing a massive amount of money. The former is a loss they can plan for and absorb. The latter might kill their business.
Traders are often happy to take the other side of that trade because they can trade against many counterparties, collect a small premium from each one, and try to ensure their counterparties won’t all fail in a correlated way.
Yes, it's not about onions.