You can decide to walk into an online casino with 50 dollars in your pocket and when you end up losing its easy for you to just walk out or look for something else to keep yourself busy. But an online casino is quite different, it's easy for you to keep chasing your losses, all it takes is just a click of a button to keep funding your bet account from your bank account. You can lose money online just in few seconds and if you don't control yourself you can keep going till everything in your bank account is completely empty. The percentage of people addicted to online gambling are more than offline gamblers.
50$ seems too low an amount, but many people can survive a month on this amount, and the person may save money from there. The amount is low or high is based on the person's earnings, and others might be different from person to person and country to country., So, after losing this 50$ many people might fall into a disaster.