When we can openly give thanks to others for their acts of kindness, we open the door for a deeper relationship with that person. Our reaction of thanks, causes the person who did the action of kindness or love towards us to open their hearts a little more towards us.
It is the same with God. Our reaction of thanksgiving shows Him our hearts and we now more about His heart. His great love for us almost demands a place of thanksgiving. We cannot neglect that place of giving thanks. It is not just for His benefit, but also for ours. Our heart grows with greater love as we express it.