Current 737NG brakes are made from a steel alloy called “Cerametalix(R) friction brake material”. The name gives the clue that they are trying to be ceramic/carbon like in their performance and they are much improved from early steel brake technology.
I suspect that Boeing have only started offering these a) because of IGW variants especially the -900ER & b) because Airbus have them and they don’t want to appear inferior.