As someone who has been positive about errands, the complete absence of gems for some of us while others rake them in is making my beard angry.
It's nothing more sinister than luck, unfortunately. Errands with gem rewards are rarer than others, but everyone has exactly the same chance as anyone else of the same PH level, doing the same amount of errands, of seeing the same types of errands.
I'm PH8, and have cleared all the errands that I've been given (some of them 2-3x) and have yet to see a single gem reward, or an errand taking over 1h 45min. I'm not a naturally lucky person, so if this is luck-based, then that totally explains it
Am PH8 and have gotten gems. I really need BP so the gems were just kinda nice. I think the variety is ok, random is ok. More BP would be good.
You must be on Midoki's good side. Or maybe they want Android players to catch up. I have yet to get a single gem after completing dozens of errands. My luck stinks.