I think the main argument against volley fire was that it's just impractical. An archer wrote a comment in another thread here on HN saying that they would do volley fire for an audience because it was expected, but the leader had only seconds to wait while they all drew back before they had to shout for them to loose. An archer just doesn't have the strength to hold the bow drawn and wait for a command like that. It's a waste of energy and resources.

What we see on TV is always one completely unprotected army, and one squad of arhcers.

But in the real world if squads of archers exist, then every single army would have a protection against them. The romans had the tortoise formation, I can't believe this was just forgotten for 1000 years.