I think mine started to do it from being bored and contained in a small room and hey, it's there, so why not
They are older and out of the 'puupy' stage and can be trusted in the whole house. So, mine have continued because of behavioral issues. They do stop for a couple of days, but then fall right back. They have jealous issues between each other, so sometimes, I think they eat it just because they don't want to other one to get.
Mine eat both dry food and very healthy human food, so that's not the problem over here, it's really become a behavioral issue now
