Buy One Get One Free

Why run a special to Buy One and Get One Free instead of offering 50% off?

I don't know the answer to this question and would imagine that it is complex and varies by business and purpose.

Could it be to reduce stock on hand. If the product is consumable will the customer have to also buy more of another companion product. For example shampoo and conditioner.

There isn't an easy way to buy one and get one free with ebooks. That is unless you have 2 ebooks and are selling them together as a set where one is free.

Could this be a new way to joint venture. Buy my product and get Mr.x's product free? Well I guess that wouldn't be too new, but not common.

What are your thoughts on this as it relates to selling digital products online?

Michael