While lots of legacy code emerges organically the way you describe, there are in fact many people in the industry who I'd call "legacy coders." People who saw Dijkstra's "Goto considered harmful" and scoffed, "all these 'for' loops are much less readable than my 'goto loop1' solution." People who use global variables because parameter-based implementations are "needlessly complex."

Basically, not everyone works for Google.