If I am using a Pok?mon on a team then yes, it will be EV trained. I don't play competitive that much and even when I do it has tended to just be matches against friends. Despite that, I want to be assured that my Pok?mon is fulfilling its role to the best of its ability, whether it be outspeeding the opponent, damaging the opponent as much as possible, or absorbing as much damage as it possibly can.
I tend to breed specific Pok?mon in the more modern games (X, Y, Omega Ruby, Alpha Sapphire, Sun, Moon, Ultra Sun, Ultra Moon) so that they can have 5 to 6 IVs, specific egg moves, and specific Natures and Abilities. Once I have the Pok?mon that fits my requirements, I EV train them appropriately at level 1 through Super Training. Meanwhile, in older games, I still EV train while raising the Pok?mon and try to go for specific Natures and Abilities but IV breeding is out the window.
I was greatly disappointed with the removal of Super Training in Sun, Moon, Ultra Sun, and Ultra Moon because I found it to be the fastest, easiest, and simplest to keep track of method of EV training. When applicable, meaning any Pok?mon that was released prior to Generation 7, I will still breed team members in Generation 6 games so I can just Super Train them and then transfer them up to the new games with Pok?mon Bank.
Again, even though I don't often play against other humans, I like to know that all of my Pok?mon are capable of being used in such a situation. In addition, I feel that, for me personally, ignoring such a simple mechanic is to play suboptimally. Why should I not want to damage the opponent as much as possible, even if it is just the in-game trainers? It would just bug me not to utilize these tools the game creators present us with.