In a - that's how I call it - warrior-based culture, the focus of a game would NOT be diplomacvy, as diplomacy would be considered "weak" and "unstrong".
Killing also eleminated to need to negotiate; as negotiation would be considered "slow" and "energy-consuming" by those who believe that simple killing is "fast" and "swift" and doesn't need too much energy - and no thinking at all. Just good reflexes.
I see your point, but I dont think that people appraise so much "warrior-based" culture. For example recent war in Iraq ignited big protestations over the world. Problem is that people are uneducated and dont care. They seek "big fun", easy money, no limits - so they dont respect anything. Diplomacy needs very different direction - inteligent and patient person able to learn, communicate with people rised from different cultures,, make own opinions based on facts (!!! - nowadays many people think shit based on primitive black/white logic and accept stupid "opinions" from mainstream media etc. - just like sheeps), respect your partner - if you are egoistic, nobody will listen to you and your diplomacy attempt will end in ruin. So "diplomacy" is too difficult and time-consuming for them. Simple-minded and egoistic person knows usually only easy methods like force, lies... And from that standpoint, ARPGs seems to mirror their needs - players can be superheroes (to please an ego), can have many items, gameplay is easy (silly) so it matches their level of thinking etc. (Note - ARPGs can be easy relax also for inteligent/older persons, so I'm not saying that ALL players are stupid)
Now they will beat me for this opinion
But on the other hand - there are situations when "force" is better solution than "words". Not everyone is reasonable and will listen to words...