You can't compare fly fishing and spin casting. When you're fly fishing you're working a stretch of river, and you're typically standing right in the middle of it. In order to not be fishing spooked fish, you need a good stretch of water in the direction that you're fishing (the direction you're fishing is another way of saying the direction you're MOVING).

I wade fish primarily, and might cover up to a quarter mile of river in an afternoon, the majority of which is directly in the water. The typical spin fisherman does not cover a lot of water, and is usually fishing from shore.

Many bait and tackle fishermen are quite content to lean a couple of rods over a bridge and hang out. Watchin the tip, watchin the tip, watchin the tip. Nothing wrong with it, but it certainly isn't irritating when somebody else throws a line over the bridge twenty feet away.

A large number of fly fishermen do not camp holes. Many of us don't even think in terms of holes. When I'm fishing I know where the fish are holding within my casting range, and I'm also eyeing the water upstream (or downstream, method depending), plotting my course. What's the safest approach, how stealthy do I need to be, and so on. It's a lot like becoming part of the stream for a few hours.

When somebody comes spashing into the water just ahead of me, it ruins the whole flow, and it becomes a game of leapfrog...which, interestingly enough, is a lot like spin fishing.

Fly fishermen who crowd are probably of the "hole" mentality. They see only the few best spots to fish on a stretch, and like a spin caster, will concentrate on them. They probably don't even realize that the guy they jumped ahead of 100 feet downstream is actually in the process of *moving*...just very slowly.

Apples and oranges on the river.