I guess for me it is is because I want an application independent and operating system independent way of getting at all my photos. This is why I am stuck in the folder structure PC mind set!
I do not want my life stored in an application database that only one application running under one operating system can read.
I agree with the observation that building a complex folder structure is overkill.
I did not realise the in retrospect obvious point that putting camera at the top of my hierarchy was redundant since camera is in the meta data of a photo.
Here's how I organize and back up my photos which (I feel) offers the best of an accessible photo archive and allows me to let Aperture manage the library...
I backup my CF cards to a DMG file named by month/year when they get full or at the end of a month whichever occurs first. I keep these duplicates of the RAW images from my camera on a large HD and I also back those up every month to an external drive which I store offsite.
Thus, if I ever need to go back to my RAW images for any reason (Aperture screws up, house fire, robbery, etc.) I can always do that.
Then I let Aperture manage all the photos that I import and work on. I organize my folders in Aperture by event/trip/shoot. And every year or for really big events, I'll create a new Aperture library to keep the size of the library manageable.
I use Time Machine to backup my active Aperture libraries in case I ever need to restore something I've done work on (so far never), and store my old, no longer active libraries, on the offsite backup drive.
Last but not least, I use an unlimited online Zenfolio account to export high quality JPEGs for sharing and which also acts as a backup of my finished product. Individual JPEGs never exist on my system.
This sounds like a lot of work, but it's nothing really... it requires the least amount of overhead in managing photos that I can think of. I'm only ever working with DMGs or Aperture Libraries... never with OS file system folders or individual photo files. And this scheme provides easy direct access to RAWs, a managed Aperture library, and a sound backup strategy.