Cache resets - Why are they necessary?

I would love to hear *why* the cache resets on maintenance/update/non-content patch days are necessary, and I'm sure others would like to hear why as well.

Every time the cache resets, major issues arise - all of you blues are familiar with the lock up and disconnect problems that many people experience when this happens.

I, myself, find these cache resets to severely hamper my enjoyment of the game for several reasons: 1) I am unable to enter Dalaran (on any character, any realm) for three days after a cache reset - that means Thursday evening after a Tuesday morning cache reset. That makes my cooking and instance dailies unavailable and severely interferes with my raid slotting, making it more difficult for me to progress and stay caught up with the guilds and groups that I work with. The other major cities are problems for the next 12-24 hours after resets, meaning that I can't just switch to another character and level them while my cache rewrites itself. I can't do any of my profession researches or transmutes, further hindering character utility and progress as well. All of these issues are caused by the lack of information in the client item cache files.

Other people who are hurt by the cache reset have these same hassles to work around, and are even more inconvenienced than I am - I know that I'm not the only one.

I don't want to be told how to fix this. Nothing that a blue has posted in the past two/three months of this issue has solved this problem. I want to know *why* these cache resets are supposedly so necessary.

Thanks.