I ride a lot on gravel. Generally quiet roads, with not a lot of traffic.
With the Varia, you can ride whatever line you like - and get alerted when a car is approaching from behind, giving plenty of warning to move right.
Without the Varia, I was either always riding on the right, or always checking over my shoulder - or sometimes not, and get scared sh!tless when a car surprises me by passing.
I was a skeptic before I got it, but I’ll not ride anymore without it.