Firearm Question: Proper scope placement?

So, I have a question about the "proper" placement of a scope on my rifle! It's an AR-15 and has picatinny rail for mounting stuff, which, obviously, is where my scope will be placed.

But my question is this: Is it more "proper" to place your scope further forward (toward the barrel) than it is further back (toward the stock)?

Basically every rifle I have seen with a similar scope/sight (red dot sight, sort of "ACOG style") has it mounted toward the FRONT of the gun. Every one.

Now personally I would much rather mount mine further toward the stock. Is there any reason why I should not do this? (And no, it can't go far back enough so I'll hit myself in the eye with it) Is it just personal preference, or is there a "correct" way and an "incorrect" way?

I don't think anyone is going to answer me, or even respond, but I thought I would just throw it out there, despite this and that it's probably a dumb question. Thanks!