My GSD almost always offers me his treat by bringing it and laying it on my lap. I give it back to him and he eats it then. I often wonder why he does this.

Because you have established yourself as the pack leader and as such, you eat first. It's only after the pack leader has had his fill that the lower ranking members are allowed to eat.

This is a good thing. :)

Yep, that is great behaviour as Alty said.

In the wild the pack leader will always be the first one to eat which is why he is making sure have had your fill before he eats his.

Aww this question brought a tear to my eye. People rarley get to this spot with their dogs! Good Job! :)