modulation normalizating factor in matlab

in matlab there is function called modnorm used in (from help)

M = 16; % Alphabet size % QAM Modulation hMod = comm.RectangularQAMModulator(M);

x = randi([0 M-1], 100,1); scale = modnorm(const,'peakpow',1); % Compute scale factor. y = scale * step(hMod,x); % Modulate and scale.

but in most of matlab codes for sim ber for ex for many modeulation tech i didn't see them using modnorm cmd

so when should i use it ?

Thanks in advance