It comes with high risk but you can earn big if your luck is on your side and stars are right !
You know that the casino kind of "wants you" to go for the parlay? In other words its a trap made for the addicted and overconfident greedy gamblers. Any marketing method is made to target some emotions and here they are. 
You may have some insider news, thats another topic but blindly going for a parlay can end up with good or bad results. Most sports betting sites do give out some strange options like goal in these many minutes or this person to get yellow card. I think these are done to diversify the market for that game and give players more options to bet on than the win loss or draw. Sometimes they can have good odds and may be worth more than parlay.
As long as luck is on your side, you will not have a hard time winning in sports betting, even if that parlay has a high payout.
Sometimes I go against my analysis as I believe oddsmaker are smart enough to fool us through their line, that's why there's always a saying in gambling that the public always lose because the public decides based on their emotion than on their mind.