There isn't just one tradition. Nose flutes are traditional in some places. Using a guitar as an accompaniment to singing is a relatively modern tradition in Northern Europe anyway (by which I mean in the first instance the offshore islands). This also goes for using any instrument as an accompaniment.

Accompanied singing with Northern European songs by now is a tradition, and it is a good enough tradition, but there should never be a sense that it is the only way to do it, or that unacconpanied singing is any kind of second best.

And there's types of music, like blues or flamenco, where having a guitar accomopaniment is much more central.

But it's always the instrument accomopanies the voice, not the other way round. (It's more the other way round with music being played for dancing.)