The cause typically depends upon the person, but the majority of trainers battle for sport with currency and pride on the line. Those who seek to test their skills as trainers take it upon themselves to compete against the gym leaders for badges. The harms generally consist of malevolently minded people who use Pokemon to perpetrate crimes and wild Pokemon, who are guaranteed to attack you when you travel from one place to another. The bottom line is, if you don't train your Pokemon and build your team, you won't get far, physically or otherwise.

[ Smart man. Not that she took him for an idiot, but this does make for some rapid decision making. Given her immediate concern is his connection with Xion -- ] I met Xion in this world, yes. You can call me Valeria. [ -- she'll do what she has to do to get that answer, her tone still matter-of-fact despite her unseen expression. It's not like she doesn't have other means of acquiring information after the fact, like observing all your conversations ever. ]