Mew is always a popular choice to include in any set, particularly in special releases that pay homage to the most iconic Pokemon and cards in the TCG
Different cards can create Lander tokens, which are artifacts that can be sacrificed to search for a basic land card and put it into play, tapped
The abilities of Gods function as long as they're on the battlefield, regardless of whether they're creatures
Once you reach the phase of the game where you can afford to do multiple things per turn, you need card draw to ensure you keep having things to do (Circle of Power, Fight On!, Travel the Overworld) or at least cards which can be used multiple times (flashback spells, Ring of the Lucii, Shambling Cieth, Relentless X-ATM092)
No one has ever been shown properly playing the TCG, but it's safe to assume that since the cards are the same, the game aspect must also exist, rather than existing strictly as collectibles