Maybe when gambling started when money was not fashionable, what they used to match were coppers, silver, gold, or things that were important to them in exchange for what they won.
This is probably what you mean, am I right? Though, I really believe that there are other gamblers who do it just as a hobby and nothing else.
What do you means that there are gamblers that just do it as a hobby? Did you mean the gamblers that just play game for fun and there is no money involved? If that is it, they are not gamblers because gamblers uses money to gamble.
Gold, Silver or anything used to gamble like that are money too. Some people can use other things to gamble too, like property. But gambling with property is stupidity to me.
All of that is gambling since you can lose something with it, but also I would say playing with imaginary coins or demo money can be gambling if you care about it. If you are in competition with your friends who will collect more money it's still gambling.