* They are incredibly powerful: Groudon's power is immense, capable of altering the landscape. Having such a being on a rescue team could cause more problems than it solves. Imagine the unintended consequences of Groudon accidentally using a powerful move while trying to rescue a Meowth!
* They are solitary: Legendary Pokémon are often solitary creatures, not inclined to work in teams. Their focus is often on maintaining balance or protecting their own interests.
* They are not domesticated: Unlike the Pokémon that can be trained and raised by humans, legendary Pokémon are wild and untamed. They don't readily submit to human commands.
Furthermore, Groudon is specifically linked to land and its creation, not rescue work. Its role in the Pokémon world is different from that of a typical rescue team member.
While it's fun to imagine a powerful Pokémon like Groudon joining the Red Rescue Team, it's unlikely to happen due to the nature of legendary Pokémon and the team's mission.