Because they taste better than the food? There have been some stories where yukkuri turn cannibal because they found out that the best taste in the world is their own kids.. (Hanage-aki's doing a story like that; Pretzel-aki did one like it too)
[We] failed a little, didn't [we], Reimu?
It can't be helped, Marisa. This was an accident.
Sweet-sweet happiness, je!