it's more dramatic
Pilots in tent are under attack. they run to there prone mecks, skip up five steps and land into there seats.. dramatic combat scene insues..
Pilots in tent are under attack. They run to there standing mecks.. drama ensues as they climb the hand holds to the full height of the mech while under fire.. dramatic combat scene ensues..
I like the drama explanation. If we're talking reality then I'm thinking moving from prone to combat stance (stand up, point guns) takes longer than moving from standing or crouched to combant stance (point guns). For similar reasons laying flat on your back or standing tall with legs fully extended reduces your potential reaction time.
