Doing it this way serves a couple of purposes:
* User's don't need to bulk out their templates with repetitive stuff.
* Stack ownership becomes transparent to users so no learning curve.
* Templates get validated as they're parsed to json (extra bonus).

I think this approach makes even more sense when we consider adding default tags to the mix. Otherwise templates would have to look something like:
``"Tags": [
    {{default_tags}},
    {
        "Key": "My Tag",
        "Value": "My Tag Value"
    }
]``