The stock market by itself has similar outcomes to the prediction markets (you buy X hoping it'll go up so you can earn $Y), but there's actual value being purchased. If I buy an apple stock, I own 0.001% or whatever of the company. If the company goes up to $10T in value, my little share is a percentage of that. I can sell it and be happy.

If the company goes to $0 then I own a portion of nothing, and so does everyone else who owns a share.

With prediction markets you don't own anything, and regardless of the outcome, someone can still win if they "bet right"

That said, futures and derivatives seem similar to prediction markets but I don't know enough about them to say more.