Entertainment is in the mindset. For instance, sport is entertaining, but hysterical fans get to cry or feel moody over a missed opportunity that led to losing a match. Over the period they'll worry about this, but months or years later they'll look back and laugh over it. However from the point of view of gamblers, their mistakes rarely allow them a time of transformation; turning it to a fun factor. It remains a lifetime sad memory for most players. Possibly entertainment has to do with an enduring memory of fun and laughter over a mistake or good deed. If a gambler doesn't have this recurring memory of constant happiness coming from his gambling experience he's not getting enough entertainment through gambling.
There are things that do not involve money like having a get-together with friends and family. In those cases, you will find most people entertained because there is no such thing as expectation or loses from such events.
I hate to disagree with your last paragraph, but, the person who spent the most money to make this gathering happen may not feel entertained depending on the outcome of this event. Which, wholely, relies on the man's mindset. He could forever regret spending all that money on this event. Contrarily, they are players who their gambling mistakes failed to hunt them for a long time, because they didn't permit it to do so. This simply determines why many players get pissed off over their losses. They permit the sad memory to recur in their mind. But that doesn't mean the anger of losing in a game would be swept away easily off our thoughts. Over a period of time, we all have the strength to cancel this painful thought from disturbing a peacefully made up mind.