First off, you need to accept that the Bookies must come out on top overall. If they didn't, then there would be no betting at all, because nobody would be able to make a living by being a Bookie.
Think about it this way. If you played a friend at coin tossing, after 100 tosses it could easily transpire that, because of the workings of the Law of Averages, neither of you had anything extra to show for it (that is, you each won 50 calls). To stay on top and make a living, the Bookies can't offer the sort of "fair" odds that apply in the case of friendly games of coin-tossing.
If the Bookies offered us "fair" Odds for soccer betting, then in order to be able to make a decent living they would have to defy the Law of Averages. The only ways for the Bookies to do that would be for them to be either clairvoyant or in bed regularly with Lady Luck.
Of course, no Bookie is clairvoyant and Lady Luck is far too fickle, so for those reasons the Bookies have to resort to introducing a "mark-down" on the "fair" returns otherwise payable to Bettors. This "incentive allowance" for the Bookies is built into all the Odds offered (Fixed Odds or otherwise) and is known as "Over-Round" in the UK and "Juice" in the USA. What matters most is exactly how much is being siphoned off by the Bookie's "mark-down"!
You owe it to yourself to get the best possible Odds for the match each time you place a bet, so it is worth shopping round to see which Bookie is offering the highest Odds for the specific match calls you wish to make.
Do bear in mind that the Bookies hate "Favourites" betting as much as you do, so what they do nowadays is tempt you to bet on the most unlikely result by considerably increasing the Odds on that unlikely result and correspondingly reducing the Odds on the most likely result. The net effect of that is that it makes it much harder to make any worthwhile money with Favourites betting, but going for the opposite calls doesn't help you out either, because the non-Favourites don't win so often!
Although it is true that at the time when they publish their Fixed Odds the Bookies have no insight as to how the bets will be spread across those who favour the Home, Away or Draw calls for each match, it doesn't actually matter too much to them. Provided that their average Over-Round is pitched around the 7.5% mark, the Bookies will continue to make around 6%-7% on total turnover over the course of a typical season.
We have the ability to carry out multiple runs using our computerised soccer prediction Program, and that has shown us that, even in the worst case scenario, a Bookie offering Odds with just 7.5% average Over-Round will make near enough 5% profit over the course of a full season.
On the evidence available to us, the Bookies' general Over-Round of 7.5% for Fixed Odds soccer betting can be considered as reasonable for "singles" betting, although at 5% Over-Round they would still do nicely. Sadly, no Bookie has been brave enough to reduce the Over-Round on the individual Odds for "parlay" (accumulator) betting, which really is necessary to stop the compounded Over-Round on combination betting from becoming prohibitive!
So what is the point of accumulator betting from the Bettor's side? Well, if you haven't got much money, then accumulator betting offers you the opportunity to earn a lot from accurately predicting all the match results in the combination line, because the winnings from all the matches combined are all multiplied together. It is especially useful when the matches you favour betting on are all being played at near enough the same time, so you wouldn't be able to wait to see the result of the first match before placing a portion of the winnings on the second bet.