A challenge in astrophotography is that the stars in an image are orders of magnitude brighter than most of the objects you want to image. To get a good pic, it's very easy to set the exposure time (or gain) high enough so that the stars oversaturate and just end up as white specs instead of their actual color (or worse, cause imaging artifacts).
A larger FW depth means I can turn my exposure times and/or gain up and capture more of the detail that might otherwise be buried in the noise.