The reason is that we do not have the right kerrnels for a froyo port. We have a .29 kernel, and we need a .32 kernel. Now, one may ask, where are the .32 kernels? So, the reason that we dont have .32 kernels that it is "an uphill battle" as described by ejhart. Since we have a .29 kernel as stock, it will be difficult to recreate a .32 kernel from source. I have also heard from ejhart that he and their team are working on a .32 kernel from the desire.
So, froyo will come with the proper kernel.
I hope this helped anyone who doesnt know why froyo isnt coming as soon as you would like. I know everyone, including myself wants froyo, and is very impatient about it, but really, do you want to run a terrible froyo rom with nothing working (or just be bootlooping) or do we want a usable froyo.
HAPPY HACKING!