If you are a league follower, know the stats, who is in form etc, this not a gambling!
Gambling is when you play roulette and anything can happen.
Betting sports is gambling, by definition, gambling is play chance for money, and even the word itself Bet (betting on sport) Gambling is not limited in Casino only, nor playing luck/chance game. The same way they tag poker and blackjack as gambling games, so is sports betting because of the word "wager for a stake".