Yes, you must complete missions, get badges or defeat enemies to get rewards.
What other playstyles are you speaking of? Are you stating that standing around pocket d roleplaying should grant rewards?
Or are you stating that the guy running at +1/x1 with SOs should get the same rewards over time as the guy completing the same mission in 1/10th the time? And if so, how is that remotely fair to anyone? Why should I be punished?