>>53161700>>53160690EVs should be changed simply because of how counter-intuitive they are.
If you're KO'ing Machokes with your Gardevoir because you're intelligently taking advantage of the type match ups you're actually screwing over the growth of your Gardevoir in a significant way. Because it gives Attack EVs, which Gardevoir can't make use of. And those Attack EVs potentially take the place of EVs that you'd otherwise want to be SpAttack or Speed or Defense.
Its simply a poor mechanic from a game play perspective.
It favors unintuitive play were you send out your Defensive monsters only against other Defensive monsters until you're sure that you've filled out enough EVs to not screw yourself out of a potentially important stat boost.
If anything it should favor a "if you do X a lot, it increases stat Y" format.
Where what you actively do as a player shifts the EVs that you acquire. Physical Damage moves give you more Attack EVs. Special Damage moves give you more SpAttack EVs. Defense boosting moves give you more Defense EVs. Recovery and healing moves give you more HP EVs. Etc.
At least those are intuitive to understand and are similar to systems used in a lot of other RPGs.