Here we go again...
Probably because it is not necessary. Lag is extremely rare in this game even when playing with or against Asians.
For you maybe.
But for a lot of other people, lag is present on a regular basis, especially against asians.
Myself included.
You might have been lucky to get matched with people that didn't lag.
But nevertheless, lag is a thing in this game.
Don't be so quick to brush it aside.
Nintendo had no idea whether or not Splatoon would be popular, as it was a new ip on an unsuccessful console. If Splatoon sold 100,000 copies worldwide, how could the game rely on regional match making? I personally think that worldwide match making was the best route for Nintendo to take, even when there is a slight delay across continents(which I admit is a bit frustrating). Hopefully regional match making is in the works for the next big update though.
Of course, this is understandable.
Nobody blames Nintendo for that. (At least I am not)
But Splatoon sold beyond their expectations and the community has grown a lot.
Splatfests prove that continental matchmaking works.
Admittedly, it takes a little longer to find people.
Plus, the fact that all people from one region are split into two teams during Splatfest, only adds to the waiting time.
(Tho in normal Turf Wars, this issue wouldnt be present)
The community has grown big enough. So yeah, regional matchmaking no longer is an unthinkable thing.
Of course, this might go against Nintendo's wishes, to build a worldwide player base.
But there is no sense in that, if it is crippled with lag, due to the large distances.