Manipulation does not change it into gambling.
The mafia has never needed to cheat in a casino. The mafia would cheat but that is another matter.
Greed in the markets leads to cheating all day long.
Stroke of a pen and you can lose everything. Still not gambling. Gambling is a very specific thing based on classical odds.
The term matters because if you do not understand that you do not follow the business you are interested in.