Now my question for the casinos which label demo mode playing as 'fun' is, does it mean that those who place bets with real money are not having fun and are just after chasing for a chance to increase their staked money, or what?
Well, it is tag as for fun because in demo mode there's no money involved, so there's nothing to lose. Experience the game to gain idea while not risking any money but solely to have fun. While in real game, there are pressure if your goal is to profit.
Some gamblers are focus on this goal rather than enjoying the game and rely on their luck. Especially those who are not prepared to lose, it became a game with an expectation to win and not playing to entertain themselves.