The Makedonian phalanx -- why such depth?

[PMBardunias]

...Archelaos, standing to my left can't believe his luck ! A helpless target, pinned and jammed between Me and Giannis shoving from behind, unable to move. While keeping his own opponent at bay, he angles his spear to the right and gives a quick thrust.....Horrified you see it coming but can do nothing.
'The pitiless iron slams though your neck,' ( to coin a Homeric phrase !) the point severing your carotid, and all but severing your spine as it is as quickly withdrawn. Giannis, spattered in your gore, scrambles backward to avoid a like fate. Archelaos and I push forward, only to be driven back in turn and the two sides separate in this immediate vicinity gathering breath and strength for the next onslaught.....

Except that he has a spear that extends some 5' beyond his grip and I am within 3' of him. His spear is quickly bound up with Giannis' and while he is looking sideways the hoplite in front of him is slamming into him with his own aspis and, more importantly, inserting his short laconian xiphos into the soft flesh between neck and clavicle. A veritable fountain of gore spouts forth like a red rooster tail..

The point being that the presence of nasty sharp weapons renders any attempt at 'shoving', even for a short while, suicidal.....

This is not even debatable. We KNOW that men came shield to shield in some battles. I'm not sure why you are argueing this tack. They may very well have not pushed at all and alaways fought at spear range, but that would be as much the result of specifically not closing as closing would be intentionally coming to grips.