Jaxx had done that since puppy hood and he is going on 9 now.
He doesn't seem to care what "present" he gives to me, just as long as I take it and praise him for the beautiful gift he is happy.
The gift giving is always accompanied by the famous happy dance with loads of nubby wagging
I have no idea why they do it, all I know is it makes me smile every time so it is perfectly fine with me.