By spreading, I think you're referring to interleaving https://en.wikipedia.org/wiki/Burst_error-correcting_code#Interleaved_codes https://en.wikipedia.org/wiki

By spreading, I think you're referring to interleaving https://en.wikipedia.org/wiki/Burst_error-correcting_code#Interleaved_codes https://en.wikipedia.org/wiki/Burst_error-correcting_code#In... , which doesn't need randomness. Pseudo-random scrambling is used in places like https://en.wikipedia.org/wiki/64b/66b_encoding https://en.wikipedia.org/wiki/64b/66b_encoding to reduce the chances of many consecutive 0s or 1s which could cause clock desynchronization between the sender and receiver.