I do it on request. Most custom builds of late seem to be asking for it.
I don't see much point in putting a radius on a soprano fret board, but on concerts and certainly on tenors you will notice it compared to a flat board. I find that using a 12" radius optimum on these small instruments. 16" ends up just barely noticeable.
It will aid and feel a bit more comfortable for most people when they bar the fret board. It adds a few extra steps to the building process. Not a big deal if you are doing it for yourself, but expect to pay a bit extra if you are asking someone else to do it for you.