You will always lose if you will not have your experience or interest in any game and you will just follow the tips of others. It is like playing blindly. Betting is an easy game if you know about the sports about which you know like if you know that which player will perform better and how much are their capability then you will bet accordingly and will not lose.
Those who to do sport betting usually have an interest and the fans from particular sports and they know well almost every teams to bets but i think betting game is not easy such as you says even if you have good knowledge for particular teams but sometimes even favourite teams can give unpredictable results to you but indeed the difference if you have at least small knowledge then you can predict by with yourself the results of matches
Yes sometimes it happens but it do not happens all the time, in sports we know that which team is doing better against another and sometimes we see a two great teams facing each other so in that match the games becomes critical and we all who spend time in sports know about that and we know that which are those teams who show unpredictable results which make the betting predictable for us. Many stronger gambler involve in that games but many often do not involve and just become the spectators of that games to secure their money from lose.