Why aren't you able to play all champs in practice tool?

I just got dumpstered by an AP Volibear toplane and his endless lightning bolts punches. That is fine, whatever, I'm Iron and I didn't know what the champion did, but why can't I enter the practice tool to see his spells in action, understand his cooldowns, etc? That's a complete joke.

I'm not going to spend the 100 Blue Essence I gain every month (another joke, btw) to understand a champion I don't play. This is so frustrating for new players, you have no idea.