I have a question.

I have been trying to understand the functions of certain elements in cake do (what does butter do? what do eggs do? etc) to learn how to make cakes come out the way I want them.  So, I've been wondering, why add jello?  I understand adding pudding makes for extra moisture and a litter denser cake (which I like) but what does jello do?  To me, it just feels like adding flavor.  But so does a bit of zest or extract.

So, is there any additional bonus to using jello?  Or is it just cost effective?  Thanks for insight!!