I have both RobinHood account and IBKR and I don't see how I could do an unhedged short.
As a retail investor, the only way I see to short is via options and there you can only loose 100%.
It also bears mentioning that an average result in Vegas is: you loose.
Benchmark returns for stock market is S&P 500 which is 8-15% yearly return (over multiple years, depending on how good the economy is during those years).
And the chances of doing better are higher than chances of loosing money.
It looks like the person in your example was selling a call, which has potentially unlimited losses - that was a rather poor decision on his part. There are much safer methods of making "the same bet".
Gambling is a random game designed to extract money from people. The stock market is a math game that doesn't care if you gain or lose.
Famous example: https://www.investopedia.com/articles/investing/121515/how-s...