If you think you have an edge in singles betting why can this not be translated into greater profits on an accumulator?
Let us suppose there are two football matches and the odds being offered on a home win are evens and that you believe a home win in both cases is a value bet. Sports betting is not like flipping a coin and so the 'true' odds, assuming such a thing exists, will not be 50% however if you believe yourself as knowledgeable as the bookmaker then the average true odds will be 50%. E.g.
Match 1 True odds of a Home win = 60%
Match 2 True odds of a Home win = 40%
If we place equal bets of say £100 on two singles then our expected return will be;
(£200 x 60%) + (£200 x 40%) = £200 i.e. zero profit/loss
If alternatively we place a £200 double on both matches ending in a Home win then our expected return will now be;
(£800 x 60% x 40%) = £192 i.e. a loss of £8
If we rework this example where we have a small edge due to our greater knowledge then if the variance between the true odds is very small then it is true we are better off with an accumulator but if the variance is not small which invariably it will not be in sporting events then disaster strikes and we will once again suffer a loss.