>>713797886
It's sort of implied through various items and dialog, but the mechanics are never made fully understood to you at any point and I don't recall anything saying 'hey beating up X gives Y' either, there isn't always a correlation between that and base stats.

>Vitamins (and feathers) making certain stats higher, but they couldn't be used over 100 EVs until SwSh
>If you get Pokerus for the first time, in most games you're told by a nurse that it's beneficial
>Macho Brace mentions it slows the wielder down but 'promotes growth'
>Since Emerald, several berries reduce your stats if used
>DP adds specialist equivalent stat-manipulating gear
>Other games may have NPC services or other features that promote growth in some manner
>Later ones have star graphs for EV distribution but never numbers

Outside of items, shit's technically tied to experience so it took until BW to be able to get EVs at Lv100 and effectively retrain, and XY to adjust the stat cap to 252 instead of 255 (as to avoid wasted points) on top of other odd tweaks overtime. For what's meant to be mostly a children's game, I must say the EV system is oddly nuanced but also opaque.