This is a war game not a spectator sport

ARGO: Even if the arty were not even in the game "it does happen...rarely" The idea of waiting out that first wave can give you a better judge on the enemies direction and offcourse your scouts are getting the size of the force comming.
Example: How many times on the map have the team all gone like lemmings one way expecting the enemy to be there and the entire enemy force just happend to take another route thus bypassing you entirely and hitting the scantily defended base in force and quickly getting the upperhand in numbers because they steamrolled right over it's defenders. Now you got to run back under arty fire or TDs and prey you can out skill them or run and cap faster.