Well, to answer the question 'why' - i have a set of Airwing bars which I would like to use and this type of convertor will allow me to use them. Normal stems do not seem to work as they mark the bars when trying to use them.
I hope this answers your query. I should mention that, when I got notifiaction of a reply, I was hopeful it was someone with a convertor; I was somewhat surprised to see the 'why'. I am now hoping that you have a suitable one, if not, GRRRRRRRRRRRRRRRRRRR!!!! lol
Richard