It is really difficult to correctly predict the combo bets because here you need to predict few bets correctly in order to win the money. Even if you lost one bet, you will lose the combo bet. So it is really risky to go for combo bets.
The only reason why people will try their luck on these bets is that if they win these combo bets, the reward will be much higher as compared to win a single bet.
If you ask me, i will prefer to win a single bet even though my profit ratio will be less but it is better to avoid the loss by not playing the combo bets.
This is an ongoing discussion and I agree that it is better to just find single value bets than to place combi bets. Yes it is a nice feeling to hit one and than the payout will also be a lot larger than compared to a single bet, but how profitable is it? I like stats and I kept track of all my bets some years ago and the main conclusion was that, at least for me, placing combo bets will not result in a positive ROI