Question

In the games they don't actually mention evs
When you get pokerus they just say it makes your Pokemon stronger
Also they don't mention effects of natures and ivs
Why - though in hg as bl and wh they do show you increasing and decreasing natures

Answer 1

They show you what the nature of the pokemon does to pokemon stats so you dont have to go look it up if you forgot.Its been quite helpful for me.Its just there for convince. And they dont mention EVs in-game mainly for the reason that EVs and EV training is used for competitive battles mostly.