Ok, I'm trying to figure out what the various societies of EP would be willing to kill for.
Based on what we know from the setting, why would, outside of exceptional circumstances, any given recognizable group in EP attack another group?
Jovians: While expansionism is a stated interest of some members of the Jovian Republic, many of their behaviors seem more defensive than anything else. Given this, I'd say their motivation list boils down to border protection and retributive strikes.
Titanians: Similarly, the Commonwealth doesn't seem super interested in raiding. However, they're more tied to external groups than the Republic. Their list is the super vague term 'Protecting Titanian interests.'
Anarchists: Anarchists seem likely to fight for purely ideological reasons. They're getting FREEEEEEEEEEDOOOOOOOOOOOOM as their primary motivation for attacking other groups, particularly groups with hierarchies of any kind.
Ultimates: Ultimates lik 2 fite. I say they'll attack someone for the sheer difficulty provided by the combat.
Libertarians: Money. Self-defense? Maybe for ideological reasons similar to anarchists
Scum: Fun. EDIT: And drugs! EDIT2: Piracy!
Martian Planetary Government: This is trickier. It's difficult to separate the governments interests from the hypercorps. I'd going to say protecting Martian citizens, but I'm not even sure on that.
Criminals: Fun and Profit!
Venusians: Ummmmmmmm... I'd have to check the book to see if they have armed forces to attack with.
Lunans: For outdated nation-states, for pride, for LUNA!
Argonauts: To preserve or spread knowledge, and to prevent major disasters.
Brinkers: ¯\_(ツ)_/¯ EDIT: MOONSHINE! Actually, just very anti-intrusion
Did I miss anything or anyone? Can I get a disagreement?
EDIT (Forgotten branches on the transhuman tree):
Exhumans: Varies. Resources, in whatever form that might take, are probably a big one. Territorial boundaries, like Brinkers or polities. Fun? Moonshine?
Firewall: X-risks. Secrecy.