To the extent that there is a liquid secondary market in trading cards, I'm not sure there is a real line between them and retail gambling instruments. But, some things cases have more in common with scratchers than Pokemon booster packs:
- They're available instantly in effectively unlimited quantity, as many as you want to buy.
- Although technically there are many gradations, the quality label of an item ("Factory new", "battle-scarred", etc.) is incontrovertible and easily verified.
- As a digital good, liquidation is extremely low-friction and virtually risk-free. In fact:
- You can click a button from within the game itself to see the current market value in USD -- sorry, in "Steam credit" -- and another to immediately offer the item for sale at that price.
- Maybe most relevant to this thread, even without liquidating they can be easily used as currency to participate in unregulated online roulette, slots, sports betting and more.
So, yeah, there are some differences.