Unlike the scrum, success in the lineout depends on the successful completion of several quite different actions by a number of different lineout units. In other words there are a lot of things that can go wrong!
Thus, attempting to coach the beginning lineout using complete lineouts doesn't make a lot of sense, there is just too much happening and the necessary focus is quickly lost.
Ten conventional seven-man lineouts -say fifteen minutes of practice time - means that the thrower throws ten times but individual supporters and jumpers may be actually involved only four or five times and the other lineout members even less. No wonder minds wander!