Easy as Pie?

So what the heck does saying something is "as easy as pie" mean? This phrase doesn't really make any sense. If I said something was "tasty as pie" then everyone understands, but what is so easy about a pie? It's not talking about making a pie cause if I had to make a pie the only part I would know how to do is buy a pie crust. Maybe people mean as easy as eating pie? I guess that makes sense, as long as the pie isn't too liquidy, or too hot, or the last thing I'm trying to fit into my stomach at the end of a Thanksgiving meal. I guess people might mean something is as "easy as pi". But that doesn't make sense cause 1. I've only heard Americans use this phrase and they suck at math and 2. why wouldn't the phrase be "as easy as addition". I propose we never use this phrase again until someone can give an explanation for it. Dropping it from our speech should be a piece of cake...