Because you may be able to sell your place in line. ...
Regardless, their commitment was delivery in 4 to 6 weeks from confirmed order or your money back.
At 6 weeks + one day I start the refund process.
I trust their competition to get the performance ramped up on their new device more than I trust BFL to deliver their already fully functional device. Sad, really, since the BFL hardware and specs look nice.
However, honesty/integrity does count.
For an example of BFL honesty, go to this page: http://www.butterflylabs.com/drivers/
and download one of the 'currently available drivers' one through four. They are claiming capabilities they are not delivering.