I think only one person really understood why a warrior would do this, or rather, why any and all classes do this:
a) It’s a valid tactic used to reset a fight. Much in the same way that a thief will stealth or use SR, it’s to provide some space for healing or to simply retreat from a fight that you are sure you are going to die in. Do you sit there and let people kill you if you have no chance? Getting away isn’t cowardly, it’s smart.
b) I’ve used GS rush and WA many times to bait people. I have picked off entire groups of 10 or more one or two at a time by having them chase, one or two getting really close, and then I swap to either my hammer or axe with a sigil of hydromancy that effectively roots them for 2 seconds and go to town. One down. Who’s next?
c) If you are not smart enough to realize when it’s simply time to get the hell out of dodge, and you’re willing to die for no reason, that’s your problem. Every player of every type of class I’ve come across has used various ways of escaping me, and it’s usually when they’ve taken a few hits they know they can’t manage long-term. Elementalist swaps to earth for stability and then air and flashes the hell out. Necro switches to lich or plague form and says cya! Mesmer spawns clones and phantasms, swaps and blinks, veils and gets away. Engi, holy crap, ever see an engi traited for mobility make an escape? You can chase one around the map ten times over. Ranger, came across one today that used his skills brilliantly. He would tap about-face, hit lightning reflexes, then tap about face again. Sword 2 and GS 3 to get guild wars 2 gold further away. He was completely uncatchable. There were 6 of us and one of him. He used his brain and evaded death while we tried helplessly to chase him down halfway across the map. Thief? I don’t think I even need to mention thief, do I? Guardians will pop Retreat, Save Yourselves, invul, and sometimes even a book not to speed away, but to stop you from being able to kill them before they get to where they’re going (usually leading you right into the group just around the corner that you foolishly chased him alone into).
A smart player uses these various methods of escape for a lot of different reasons. Oftentimes, if you see me using Rush, I’m baiting you. Come after me, do it. Break away from your group to chase me. Then I’ll turn around and crack your skull open. Your fault. Not mine.
When I first started playing WvW, I used to think the same thing: cowards. Why do they run? The longer I played, the more I understood. It’s a very simple thing: if you want to sit there and die for no reason whatsoever, I mean really knowingly die, you haven’t learned to be smart enough not to yet.