Consider casino games versus
poker games. When someone on the casino floor wins big, the house takes their picture with their winnings and posts it so everyone can see what a great decision they made to play there. In fact, anyone that plays the casino games has made a poor decision because the house has the edge in every game offered. The casino lays
odds and the players take them. Same thing applies to sports books.
In poker, you take on the roll of the casino. Your job is to lay odds that the weaker players take. Odds that will not be in the weaker player's favor if you have learned proper bet sizing. You also have to be able to spot a
bluff and be able to determine how often that's happening so you can assign odds to the possibility of a bluff. If you do your job and keep the odds in your favor, you will have an edge.
You're gonna win some, you're gonna lose some but in the long run, you will win overall if you play with the odds in your favor. If you're not winning, clean your game up. And no matter what, don't tell the fish what they did wrong, congratulate them with a smile on your face and move on to the next hand. Rec fish don't mind losing to the nice guy, be the nice guy and get your money back.
Short answer, it's not gambling if you can't lose in the long run.