Originally posted by 135steward
That increased +EV comes at the cost however of a lower winning percentage and, by extension, increased variance. Maximising growth/ROI would actually be achieved by two combining straight bets with a two-teamer.
The main reasons for parlays being considered sucker bets are that they often pay less than true odds and far more importantly most bets made in reality have -EV and in these cases the bettor is a victim of both the compound effect and increased variance.