18th century homes with knife boxes would also have had many servants.....who of course could not all be trusted.....and knives were expensive. People who had knife boxes likely would also have had locked sugar boxes and tea boxes.
The knives kept in a Sheraton or Hepplewhite style knife box would have been meant for dining. There most often would have been 2 knife boxes on a buffet, one on either end ....sort of like 19th century handkerchief boxes on a dresser....but the knife boxes were separate, not attached to the buffet....so the butler could carry them into the kitchen for cleaning.
As far as I know, only knives were stored in them.
Some where on the web is a virtual tour of Jefferson's home, Monticello. As I recall there were several pairs of knife boxes.
Linda C

Thanks Linda, so knife boxes are like lamps a pair is always better then a single.

Anything with it's "twin" is better than without....a cup AND saucer....Creamer AND sugar...candle sticks, mantle garnitures, salt AND pepper....shoes, socks....gloves....
You get the idea...:-)