Mostly they don't publish weights, because at the end of the day it just doesn't matter.
This, pretty much. Also the 154 will weigh different from the 157 and the medium bindings less than the large, etc. so then you start worrying about the entire matrix of weights and surprise next thing you know you're snowboarding's equivalent of a weight weenie
It's easier to just leave your wallet in the car if you want to shave a few grams, or drink one less beer, etc.