That's actually a really inkredible idea.

Actually a pretty amusing idea.

Of course the main reason it's not getting voice chat is due to the devs themselves having bad experiences with it. I believe the producer once said "every time I've played a shooter with voice chat, hardly anyone was ever being helpful, most of what I heard was nothing but hateful slurs and trash talk. If this is just the norm with voice chat in shooters, we do not want Splatoon to have a similar reputation."

Fact this is a shooter that IS being marketed towards kids too (most of those cheesy commercials are made more with kids in mind, while older audiences get their info from the Directs and previews from YouTubers invited to official Nintendo events), Nintendo would rather avoid angry parents calling them up asking "why did your game teach my eight year old what a 'dick sucking faggot' is?"