I have been noticing a theme with buying or using lures in the pokemon go android game. I encounter shinys and perfects primarily when my husband puts down a lure or when we piggyback off a friends lure at the park. We've noticed that my husband only gets shinys and perfects when he piggybacks off a lure I set off. It seems like lures are benefiting piggybackers more than they benefit the person who set the lure. Others on fb in one of the groups have noticed that as well.
Also noticed it in the battle league when we battle each other. The loser gets evolution items etc and the winner usually gets a crappy item or stardust. I'm kinda pissed off about the lure thing because if I'm paying for a lure I should be informed if its gonna be benefiting one party over another because it's not fair if the person who set the lure doesn't get anything good but the other people do. It makes me want to only piggyback off other lures. I get their program is random but I can't help but feel that with their recent track history and non disclosure of drop rates or shiny spawns that niantic would implement something like that in order to get people grouped together to better their odd. We all get shinys and perfects when we all set lures. I only notice this because me and my husband don't always have lures at the same time.