All barrels are not created equal and all do not come from the factory smooth & polished, free from *^%# defects. See mini -14 section on lapping the barrel or loading special bullets to accomplish the same thing but you shoot your barrel smooth.
The concept is kinda old. Has anyone ever had an average shooting gun and it's this way for years - then it starts to shoot GREAT. You smoothed it out the old fashioned way - you shot it !
If your barrel IS already perfect - congrats - now keep it that way.
Competition shooters can be superstitious folk and I will leave it to the shooter to decide which "apply" to them & their routine. But if you spent the extra $$$ on a good barrel, why not spend the extra minute to run a snake down the barrel ? (Counts as a cleaning in my book)