Why All The Affidavits?

Open Question: Why are banks submitting Lost Note Affidavits (LNA) as their primary way of claiming right to foreclose? Why not submit the original property note? Filing a LNA is supposed to be a "back-up" mechanism in the law. However, banks appear to be using it as their primary means of claiming right to foreclose.

This article states Bank of America will file 102,000 new affidavits. [http://online.wsj.com/article/SB10001424052702303496104575560432631814848.html]. Why aren't they instead submitting 102,000 original notes?

Does anyone know: Why has the procedure of foreclosure in the business model of mortgage securitization come to rely primarily on the backup legal method of filing Lost Note Affidavits?