Combination bets have their uses. The biggest challenge is that all the included events need to be successful to generate a significant profit. In practice, however, most people use this type of bet more for fun, combining several unlikely events. And that's precisely what makes it even more interesting: the excitement it provides.
I don't think that gamblers uses it for more fun, they are betting of parlays because they wanted to hit that big multiplier. So just a small bet might turn into hundreds or even thousands if you predicted everything perfectly. If they wanted to have some fun then just put a single bet and wait for the outcome. As compare to parlays, which might take the whole day and so you will be stress out from waiting what will be the result it. And what others have said, it's not yet a win until all games have been played in a parlay. And if you think that you have a better chance, then think again. Even if you have 9 out of 10 wins, there will still be that last game that might put a big dent and totally ruined your earlier winnings.