This disappearing act isn't just an artifact of the past, but a reminder: games are shaped by more than just their developers, and may undergo drastic changes in their efforts to meet the standards of many different rating boards worldwide.
Rather than a Game Corner, Pokemon began implementing its new minigames into the menu screen, like Super Training in X and Y or the curry-making game from Sword and Shield. The brand recognition of Pokemon as a children's game was also important to Nintendo, and so the minigames once confined to a casino-like building had to migrate elsewhere. The logic holds up - it's cheaper to simply remove the disputed elements from all versions of the game, rather than bother with continuously altering international versions to suit each individual region's laws. From that point on, it was a quick and painless death for the once-beloved Game Corners.
