I've seen this recommended as a DIY or as a service performed by some companies. What I haven't seen is the reason for having this done.  It looks like it would cost around $50 if I have someone do it so I'm trying to see why you would do this to a IEM that cost less than $200.  I have the Aurvana IE-3 and was wondering about the benefits of this mod.

People like to be able to change out cables. If you're a believer in upgrade cables, you might want to buy a silver plated copper cable to use when you want a brighter sound, a peak in treble. Or you might want to use a cable with better copper in it, OR you just don't like the stock cable that is on them and would like it changed out. It would be a lot easier to add a IEM socket to a pair of IEMs than hard wire a new cable onto them. 
 
Those are just a couple reasons why. Most people wouldn't do it to a sub $200 IEM though.