Protocols don't necessary assume that players are profit-seeking. Ethereum's Casper for example allows that players may wish to smash the board; however, it makes attacks very expensive, limits the damage they can do, and makes it easy for the network to recover.
Subtle ways to get extra gains can be a problem; e.g. people didn't figure out selfish mining attacks until Bitcoin was several years old. Cryptoeconomics is a new field, and it advances as people discover attacks and invent solutions to them.
Subtle ways to get extra gains can be a problem; e.g. people didn't figure out selfish mining attacks until Bitcoin was several years old. Cryptoeconomics is a new field, and it advances as people discover attacks and invent solutions to them.