While technically it could be called gambling, it's definitely not in the same league as risking real money on a bet. With virtual currency, that has no exchangeable value, you can never judge the quality of your opponent and their betting patterns almost become meaningless - so it's hard to improve or derive practical knowledge if your intention was to convert to paid betting later. As the person placing the bet, you will be more likely to take time and think through your betting strategy when real money is at risk.
Gambling that does not involve money is just like we are trading on a demo account. Those that know what they are doing will understand that it is totally unnecessary to gamble with money. Money is the backbone on all gambling activities because the money involved will make everyone to come for the money and earn some good profits. When money is not involved or financial materials and object, people are not going to take that seriously because they have nothing to lose at the end of everything. Whether we gamble rarely or often, money is what makes us want to gamble more as a gambler.
If we look at it from a guessing system, maybe this can really be related to trading on a demo account, but in my opinion this assumption is not quite right when it is associated with a demo account that doesn't have real bets in it, because gambling is very much related to money as the stake. Gambling and trading are quite similar, especially in terms of self-control, risk and psychology, but there are some differences in how to do it, but indeed it all comes back to the point of view of each person. Totally agree with what you said that money is the main backbone in gambling. If indeed there is a bet that is exactly the same as gambling but you don't see the money in it, maybe it will only give pleasure to that person without getting any consequences from the bet. Prizes or winnings from gambling are actually really wanted by everyone and it is undeniable that everyone needs money, but on the other hand not many do it because maybe the risk in gambling is very big and indeed this only relies on luck without any consistent winning streak in it. .