SNIP

My thinking is that sheet goods are made 4 feet wide, and 3 times 16 is 48.
Thus the sheet goods do not require trimming to fit framing on 16" centers.

END SNIP

Jim:

You are very close.  Although I do not recall why, modern construction
materials are designed to a 4" module; that is, standard materials are all a
multiple of 4."

J