Games are not games because they are scored and have goals. Games are games because they are fun. Scoring is one aspect and usually present, but it's only one aspect and will only appease a subset of people. You can play soccer for 2+ hours and not achieve a single goal. It's still fun. Even if goals are scored, keeping track is entirely optional. Soccer is a game and fun, even when you don't "gamify" it by keeping score.

Furthermore, "gamification" by that definition often begets "gaming" the system. Because scoring, measuring, and mechanical details almost never perfectly match the spirit and original intent of the game, these edge cases cause dissonance and frequently disengagement. Examples: A baseball player hitting 17 foul balls waiting for a good pitch, basketball players causing fouls on purpose simply to stop the game clock, monks in Everquest using the "feign death" skill to split mobs that would be unbeatable as a group; these are real dynamics in successful game systems originally designed or evolved to be that way. In other areas, such as academic grading or pay-for-performance, the dissonance is significantly more profound.

People play foldit because it's fun, and that's what "gamification" should be about. The scoring metrics are merely a small piece of that.