This is one of those instances I have to spell this out for any math-oriented readers.

About 20 years ago a famous Pennsylvania bookmaker went to trial because, well, he was a bookmaker. His name was Mike Stockunas (you can look him up -- it was his first trial; not the second). The prosecutors put his assistant on the witness stand. They put the assistant under oath, and one of the prosecutors asked him, "Do you know what a parlay is?" The witness answered, "Yes, sir, I do." There was a pause. The prosecutor continued, "Well, would you tell us what a parlay is?" The bookmaker's assistant answered, "It's a really stupid bet."

And that is the truth in 99% of the cases, no matter what you hear. There are certain rare specific situations when it may make sense, but in general, betting parlays is either a sign of being stupid or lazy or both. I suspect most of the time it's laziness.

One of my partners from decades ago bet boxing almost exclusively, and usually for large sums. He characterized parlay bettors as "poor people trying to get rich." So I guess I'd add that to the description. If you're betting parlays, in 99% of the situations, you're tipping people off that you're either stupid, lazy, or poor.