I can weigh in on this because I was spread betting for 10 years. All I did was play the FTSE 100 every day. I spent months understanding how it moved and played that, so when it was high I'd put a position on that it would go down, when it was low I'd bet it would go up. To me it never felt like gambling because I understood it so well.
I turned £3000 into £60,000 in a year, and the spread betting company started taking me out for meals, offering me tickets to big sold-out events. I thought I was an anomaly that couldn't lose. For 2 years straight I didn't have a losing position, my account just kept piling up. I earned way more in this than in my day job.
But..... all it takes is for a big-scale event or a black swan event as it's known. Something hugely unexpected that will change the market and you're absolutely done for, in this case it was covid, something pretty unpredictable. I lost about £75,000 overnight. the Russia/Ukraine war did the same thing.
No one knows when these kinds of things could happen and the markets can dramatically turn in seconds and you can't get out.
You can have stops in place, but I assure you you'll move them. And your losers will get bigger and bigger and bigger.
It's dangerous, the leverage is dangerous, you'll get very addicted to seeing the money pile up, but you'll start to lose sleep when things get bad.
It's hard not to look back and think of what I could have done with £75,000 but it taught me a very valuable life lesson. Keep your investments in the smart places that make 5-10% a year. Spreadbetting is as good as going into a casino and betting your life savings on red or black.