You seem to be overlooking a huge thing - collectibles have an (above-the-board) resale value. While perhaps the market crashes someday, for 25 years Magic cards have done nothing but go up in value. I'm personally up tens of thousands of dollars lifetime from paper Magic, and some thousands from dabbling in digital. And all of it was purchased for play, not investment.

Non-collectible virtual goods have dubious resale value. You can technically sell game accounts I suppose, but it's inevitably against Terms of Service and commensurately difficult.