read what i wrote above and your 'problem' is solved

the reward is the community and the friendships you make. 'earning' hours isn't something that deserves a material reward. how would anybody measure how much of an achievement it is to take a tower with a mass of players?

while doing solo stuff like for example the bounty quest, you kill a certain amount of baddies, that deserves a reward because there is a well defined trade deal going on. YOU made a performance so YOU are rewarded