Numbering systems

I know I have blogged about numbering systems before...but... Can someone tell me the point of having the volume, number and whole number plus the date all for enumeration? Or for continuing to use two numbering systems for more than a century (e.g. Old Series Volume and Number, plus New Series Volume and Number)? Or for just abandoning all numbering and changing to month and year only (without any notice, of course)? And is there any sensible reason to change a publishing schedule in the middle of the volume, but with the same numbering but different chronology (thus making predictions and MARC records near to impossible!)? Do the publishers make rational decisions on these things or is it at the whim of the newest editor du jour? "Inquiring minds want to know...." (if you grew up in the 1980's you'll recognize the reference to bad tv commercials for the National Enquirer)