Bit scrambling as last state of transmitter - what advantages are there?

I believe that I read, for digital modulation with multiple levels, that the AGC makes use of the fact that the symbol sequence, before noise etc., can be modeled as a uniform distribution.

$$\text{Source \rightarrowsource-coding \rightarrowFEC\rightarrow interleaving \rightarrow bit-scrambling \rightarrow modulation \rightarrow channel}$$

What other advantages are there to bit scrambling (not for privacy/security).

Chris.