The mellow flavor and how easy it is to rip/eat? I often wonder if they also like it because it does have a higher water content, which in the wild finding such a food source might be helpful. Then with rescues it's all the animal knows to eat because keepers like to feed it due to it being: a) easy to find at any store b) fairly cheap c) it holds up well in your frig where many other greens don't last as long.