system
Given the following post, respond as if you're commenting on Reddit:
human
[Pokemon] If a Pokemon does little to no battling, do they stay unevolved until death?

Evolving for most Pokemon seem to just be aging to a more mature form, but unlike humans, they mostly evolve by leveling up. So if they don't battle, would they just stay their pre-evolved form and age in that form?

There's a Pikachu named Puka that aged without evolving, but Pikachu needs a thunder stone to evolve, so one can argue that Raichu is more a mutated form by absorbing the thunder stone's power, while aging as a Pikachu is more normal.
gpt
It's possible. It's also possible that a Pokémon will simply choose not to evolve, like Ash's Bulbasaur and his Pikachu. Or a trainer will choose not to evolve a Pokémon, like an Eviolite Chansey in competitive.