I recently watched a trout video called "Feeding Lies." One thing I hadn't appreciated before watching this video was how complex subsurface currents can be. They can actually go in the opposite direction of the surface current! The trout actually face downstream!
I think such complex conditions might be more common in the rocky, small water freestoners we fish here in the east. I mean, it would be nice to fish big water sometimes, but you work with what you've got.
The light bulb that went off for me was that a nymph can't be moving naturally under a strike indicator when the subsurface current is radically different than the surface current.
So there might be a real reason to fish without a strike indicator -- not just that it's more of a challenge. When the subsurface currents are complex, you can get a more natural drift and be more effective.
Think there's anything to this?