This is an example of the difference between "Charity," and love/kind acts by man IMO.
Charity is the perfect love of God. He gives it freely, and without being asked, AND expects nothing in return. Not even an acknowledgement of what He has given. John 3:16 tells us how much He loves all mankind.
Kind acts, or the love man gives usually comes with expectations. As you stated, the person saying thank you for (fill in the blank) ___________, and possibly, acknowledging again the kind act after it was received/consumed.
Men/women give love, but they also expect that love be returned in some form. We can "love" many different things. I LOVE blackberry cobbler, BUT I am not very charitable towards it, because I'm gonna eat all I can of it!
Even parents loving their children expect some sort of response from that child. Yes, we may well love our children regardless, but, in my experience, IF that love is rebuked or ignored, or not returned, our depth of love begins to wane over time.
Charity! Gods perfect love! I am not sure man can ever achieve such love while here in this world in our earthly bodies.
Don't let your right hand know what your left hand is doing says the Scripture. This refers to doing charitable acts WITHOUT people knowing the acts. You are right to do them in secret, Jesus said if we receive the recognition of men for our charitable acts, then we have received our reward already. Charitable acts, dare I say works,
done in secret will be rewarded in heaven.
Lynx is correct also, in that we should not do charitable acts "expecting" any recognition. However, man is not a perfect being, and this is why I believe man can not achieve the perfect love that God gives.