From what I remember, the point is to discourage POS hugging shit and the tactics and attitudes that lead to many 0.0 alliances having all their players dock up and spin in station while any hostiles are within 18 jumps. It's shit and boring for everyone.
So "contribute or leave" means that while you may die if you fight, you surely WILL die (and lose all your shit) if you turtle consistently. As most any individual, corp, or alliance can tell you, by fighting (and, yes, dying) you get better at EVE. You refine tactics, setups, and reflexes. With mass limits and effects, small groups with situational awareness can easily screw with big groups.
Most roams are set up with generally useful setups (typically armor fleets) that don't exactly do well in certain systems. Roams also don't know the state of any holes (this problem is even worse with recent changes) so their aggression can be used against them with judicious mass transfer. Split fleets that have lost key elements are very easy to deal with.
"Perfect" setups require co-ordination and the right mix of ships - 2 faction or officer fit Bhaals are a deadly threat, but 1 which has minimal support is a really nice KB ornament. Perfect setups are also loot pinatas. When I was in AHARM the standard PVE tengu was stupidly costly (back when you could solo C4s) and the PVP fits were almost as nice.
I think it's a good ethos and helps prevent w-space from being the same stale crap that so much of k-space became. Take advantage of the resources, but don't just milk isk, make it a fun and very different part of the game.









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