They allow them to be placed on their marketplace because they dont see it as gambling in their eyes
Lets trim that down
Every reprint has repurposed art to match its respective story, and each deck tries to capture certain iconic events, characters, villains, etc
If you want this card for yourself, youre looking at anywhere from 25 to 30 for the Full Art version of Tyranitar EX
Even so, you can be sure that loads of collectors have at the back of their binders a complete set of art cards, as well as other out-of-game extra cards like tokens, checklists, and punchcards
For example, trade a card for 1 thats slightly better, then trade that card with someone else for another thats slightly better, and so on