Back a bit, before sports gambling was legal, their were ways of making bets on "cards" (minimum 3 game parlay) for nfl games. I was a student and had a summer/PT job at a box making plant, and did well a few times in the weekly plant pick'em pool, so they gave me access to these cards.
Since this was before FA (late 80s), it was much easier to pick games, and for whatever reason, the NFC East always had easy picks (and Arizona just blew). So I could do 3 or 4 cards with 3/4/5 picks and always win one but sometimes win 2 or 3.
I thought it was just great to make a hundred bucks or so extra a week. I had this winning streak and then won on the higher paying 5/6 payouts, so I was happier, made more money----and got invited to "the bar" by my source. I went, once, it was kinda rough place, met a few folks who seemed aware of my "luck" and made many comments about my age(~20) and health. I quickly realized that they were vetting me, and that I'd had little chance of collecting a bigger payout because I was a lucky kid and they were a large group of tough guys running an illegal game.
So I cut down to smaller cards, they allowed me to keep winning, and I literally paid a big chunk of my university education thru football bets. I was actually grateful for the continued access. But it was always really clear to me that there was never a path to collecting on a huge win.
Seems like things have not really changed, but the marketing is much better!
Side note: I met John Candy's brother (Brian, I think) at that bar. 30 seconds of weird intro to the bro of a really famous guy. Bizarre.