And all the important work is done in rehearsal under the leadership of the conductor (in larger ensembles, which 24 or so players would qualify as). If the conductor doesn't organize where those improvised solos take place, who's doing them, how long etc. it would be a complete mess in the performance. Mediocre players can play in an organized way with a strategy/tactics. DC does not do that. Lower middle of the pack players playing with no strategy or coherent tactics results in bottom of the league performance. A conductor, err coach with solid and coherent tactics will get more out of the players.