First, let's be honest, ALL internal combustion engines burn some oil. If they did not burn oil, the rings would be sliding up and down on dry cylinder walls. It should not be noticeable, on the dipstick, being that over about 6K miles it equates to about 1/16 of a quart.
Second, the oil filter contains more oil than you believe, even after you drain it. In TN, we had a hydraulic oil filter compressor that squeezed the oil filter down to about 1/2 inch in height, about 1/4 of a quart would be squeezed out from the filter media.
Third, there is some oil left in the engine that will not drain out. There are valleys and nooks where oil lays, as well as the bottom of the oil pan. How much, I'm not sure.
Fourth, when someone adds six quarts of oil to the engine, possibly a sixteenth was left in the oil containers. As you know, it appears these puppies will drip forever.
Desert Dan has the correct answer...watch your oil as you drive over a period of time.