So long nobody out a gun on your head, nobody sent you a malicious link and pretend and was able to take money from you, gambling is never a scam. It's simple tricks of risk to get more money, that's how gambling work. You just have to either adapt to it or you don't but there is nothing a person can do with gambling and thinks it's scam unless you win money but they refused to pay you, or close your accounts for no reasons or just hate comments.
If you gamble and you lost, know it's your loss and if you gamble and you win, then it's your win, there are no two ways to eat and beside, gambling didn't start today, it started way back before out the internet came but some of these things has been digitalized where it's more easy and accessible for everyone but not everyone is playing the safety when it comes to gambling, some people don't have self control most especially when they see their favorite game.
Exactly, bets would be a scam if your funds are frozen without reason, if you win and your bet disappears, if the game is rigged, or if it pays less than it should—it could be considered a scam. However, I don't fully agree with the notion of "nobody put a gun to your head," because it confuses a scam with theft. Scams are deceitful situations where people fall victim innocently.