In order to win at sports bets it is not necessary to do something that extreme, the house edge changes depending on the matches and the specific bets you are making, but it can be overcome if you can predict which team is going to win at a percentage slightly higher than 50%, and while this will not guarantee that you will win all the time, if you have a good money management strategy then you could eventually get profits over the casinos.
Sports betting is all about finding value bets where you think the bookie is wrong is his assesment of the match/bet line. It seems easy but is really hard and to have a positive ROI year after year, is only given for a couple of people.
And you are right, in a way it is similar to trading, trading seems to be awfully simple as you only need to buy for a low price and sell for a higher one, and despite this apparent simplicity very few people can become profitable long term, and something very similar happens with sports bets, finding value and having a skill slightly above average to pick winners are both necessary, and while in theory this may seem easy it is something that is incredibly hard to do.