For one, unlike certain other pack-based online competitive games, spending money doesn't really gain you any meaningful advantage: there's no online transfer market, for instance, where you can hawk your wares for in-game megabucks to then buy an otherwise unobtainable good squad
Usually, they cannot be Special Summoned, and have an effect that returns them to the hand during the End Phase of the turn they are Normal Summoned or flipped face-up (or the turn they are Special Summoned, in case of Spirit monsters that must be Special Summoned)
Veni veni venias, ne me mori facias...veni veni venias, ne me mori facias
You can only use this effect of "Tuning Gum" once per turn
That celebrity influence and Pokmons global audience have ensured the franchises longevity and explosion of value, according to collectible experts