Why doesn't Mr. Lapham do much silversmithing?

At one time, Mr. Lapham had been a fine and talented silversmith. He had created a silver tea set for John Hancock's uncle. When he first viewed the pitcher from the set, Johnny Tremain had never seen anything "so intricate and beautiful as the woman with folded wings whose body formed the handle" (Johnny Tremain, page 16). He wondered who had made it. He thought that the delicate and detailed pitcher "must have been the work of one of the great smiths of forty or fifty years ago." Mr. Hancock pointed out the mark, which indicated that Mr. Lapham had indeed created it. Now, Mr. Lapham's hands were not what they once were. The older man gazed "down at his own gnarled fingers" (page 15).
In addition to Mr. Lapham's physical limitations as a silversmith, he also failed to listen closely to the orders of his customers and wrote down the specifications of their orders incorrectly. This caused him to make items differently than his customers had intended.
More and more responsibility fell on Johnny's shoulders as he became a skilled apprentice. Johnny took over the responsibility of recording orders because of his master's mistakes.