Yes, sometimes expectations do not match reality and that is a consequence that every gambler has to bear. Whenever you win and have withdrawn your balance to your wallet, then invite your friends to have fun, it's much better than promising before winning. But however, this is not obligatory if he says it like this: "If I win, I'll invite you all to party".
They must prioritize reality based on gambling results rather than relying on probabilities and expectations that are not guaranteed to be obtained from betting results, even gambling experts state that there is no exact accuracy in gambling results and any opportunity to win or lose can occur at any time. So I agree with you, make sure you have won the bet and the money has been withdrawn to the bank or personal wallet, then you can make a personal decision to share the winnings with friends or buy whatever items you like, make sure you are wise in managing the winnings and it is better to never deposit all funds again into a gambling account balance.