It's not a bug. That's the way it's done. It's not logical, but that's what the developers have said several times.
Because if everyone had the option to disable it completely they would, and then when an intermittent bug happens there'll be no logging. Higher values produce more detailed (and larger) logs. The main reason people want to disable it completely is a perceived performance gain (or reduction in performance hit) even though there's no proof it would help because 1. You can't disable it to test and 2. Everyone running the game across all sorts of hardware without performance issues has the logging (see 1.). This doesn't mean no one is having any issues; but the logging is intended to help with understanding why. Whether it's actively being utilised right now, or would be missed if it were removed, is a fair question. But, if it's causing no issues, there's not much to be gained anyway.
