There are a few reasons why this might be the case:
* The game is a hack: Pokemon Ash Gray is a hack of the original Pokemon Red and Blue games, and the developers may have chosen to leave out certain items like Leaf Stones.
* Balance: The developers might have decided that including Leaf Stones would be too powerful or disrupt the game's balance.
* Storyline: The game's storyline may not require Leaf Stones, and they were omitted to maintain the intended experience.
Alternative Methods:
While you can't directly obtain a Leaf Stone in Pokemon Ash Gray, you can still evolve some Pokemon that typically require a Leaf Stone using other methods:
* Leveling up: Some Pokemon, like Gloom, will evolve into Vileplume when they reach a certain level.
* Trading: You can trade with other players who have Leaf Stones and obtain the evolved forms of Pokemon that need them.
It's important to note that these alternative methods may not be available in all versions of Pokemon Ash Gray or may require certain conditions to be met.
If you're really interested in using Leaf Stones, you might consider playing a different Pokemon game where they are available.