In sports betting, no matter how we know the capability of players, there are still unexpected occurrences that could provide us an unexpected results same as other games.
It is true that the luck factor is present in sports betting too, but it can be decreased to a great extent through skills which is why it's possible to beat the house in the long term in such games based on my research.
Most sites usually employ strategies like restricting/limiting bets in order to protect themselves in these cases.