The whole resurrection goal feels really odd to me. A lot of the other cupids seem like they've been in this industry for a long time. Is the amount of karma each cupid need to collect different or something?
There's also survivorship bias, we probably won't see the cupids who chose to revive nor hear their motives or how the process was like for them.
And the system is self-sustaining, if there were no cupids left the new generation will form naturally, continuing the cycle.