You humans are ridiculous.
"Rulers of the earth" this, "most developed species that", hah! The sheer arrogance of your thoughts is enough to send the youngest of our number into peals of laughter. To think that you believe that we follow your commands and live as your companions because you have subdued us is ridiculous in the extreme. You might as well say that you had conquered the winds or the ocean. We psychics don't need you humans for planning or to teach us how to battle. We know those things from the day we are born. No human needs to explain to an Alakazam how to use his psychic abilities effectively any more than they need to teach a Pidgey to fly.
Nor do we obey you because we have need of your food, or because your Pokemon defeated us in combat. It would be elementary to escape should we wish to the moment you released us from those spheres which you have such confidence in. After all, the only thing an Alakazam needs to travel is the power of his own thoughts. A single whim, acted upon, can transport us from the side of a would-be trainer to the base of a mountain miles away or the depths of a forest. As for food, gathering berries is never a difficult task- and we barely need to eat anyway.
Nor do we require you for intellectual stimulation. The greatest of human chess players could not hope to defeat an opponent who could do as we do and see into his mind. No human has the psychic defenses necessary to conquer one of us who sets his mind to it. We have our own language and our own ideals.
So why do we travel with you? Why take a position so easily misunderstood as a servant?
The reasons are myriad, but they can be summed up in a simple phrase: you humans intrigue us.
The reason we allow you humans to 'train' us is not because we need the training.
The reason we travel with you is because we're bored- and you're interesting.
You fight, you live, you hate, you love, and you make music- some of the best of any species that produces it. You build cities, knowing someday they could topple to the ground. Some of you even have the gall to assume you're the superior species. Hah! A species with such conceit and the gall to act on it is one that provides an endless source of amusement.
So I'll continue to travel with you. I'll give you guidance and assist you in your battles. I'll help you achieve your ambitions.
I'm bored. I have time to kill.