I use a tongue scrapper every day. At least in the morning, when in the mood on evenings too! helps where brushing / brushing & mouthwater alone dont help. The tongue plaque has become less and less over the course of time. I notice a better mouth taste and less stinky breath through out the day. (And, I kind of started to like gagging. The sound is funny. My wife laughs, too.)

once i had a collegue, he didn't like to even touch a brush, let alone, to brush his teeth once a day. So he stopped it when he was a teen. Some 30y later, his few teeths left are completely faulty. I stop breathing when talking to him and avoid standing still so i can always change positions to gather some breathable air. But he's a good guy, father of 4 girls - and became kind of a friend over the last 15y.

So, the answer to post's question is "not necessary". Mouth hygiene is only for not to feel ashamed/uncomfortable when assaulting people around oneself by a thing one can't stop - breathing and talking. If one dont use a tongue-scraper, one still can have friends and people to rely on. "Its the character, young man.." :)