Only for travel, and to keep them close incase trouble does arise. The necessity I've said, though I can understand why to someone not familiar could find even that much cruel. When not on the move people tend to keep them out of their pokéballs to roam freely. [Clavell kept his own in hand-] When I am not out, even here, mine have free roam of my home and yard, and stretch out when outside and resting from travels.

A pokémon doesn't stay in the ball if it does not wish to. [Then, a small tip of his head.] Eevee -your new friend there- is so tame because it was in a ball, which means it briefly belonged to whomever caught it, unless it hatched from an egg someone was taking care of before ending up in a ball.

Wild pokémon are not so calm, and not so friendly. They can even be dangerous, usually the fault of someone walking into their territory. Others attack to test the strength of a person if they have decided they want to see what it is like to be partnered with someone.

[A flick of his wrist, and the pokéball in hand was activated, sending out a pokémon that was quite larger than the vending machine; Abomasnow taking the time to look around after spotting Clavell, rumbling lowly as the pokémon settled. The air growing a bit chillier from his presence—]

And, perhaps to circle back to necessity- I can't very well carry Abomasnow here without a pokéball due to his size. If anything ever happened to him while not in a town, and I had nothing on hand to help him, I wouldn't force him to walk to the nearest place to heal him.