You're not sure how to feel about getting a pokémon.
It's not that you aren't grateful. But, you never asked for one, never considered it—though when you battle Cheren and Bianca, you win both times.
(You weren't trying to win. But, they both seemed impressed that you did.)
Juniper says you three are going on a journey, to help her record information on Unova's pokémon. You've never left Nuvema; and, unlike Cheren (who's wanted to so badly that some days, you believed he might run away) and Bianca (shot down for even mentioning the possibility), traveling isn't something you ever contemplated.
But, while you never asked for a pokémon, it's not like you'd give yours back. So why not go?
You meet at Route 1—Cheren, dying to race ahead, mind teeming with future plans; Bianca, hardly able to believe the reality of the present moment. And you...
Well, your mother handed you a map. Go, she urged.
So why not.
The three of you take your first step together. After that, it's all one big race to the finish.
(And you, lucky you; you're always winning.)