We drive from the PH almost all the time. We have used the FB on a number of occasions, actually more than we had anticipated. Region makes a big difference.
Here, even if it isn't outright raining, it is a bit chilly up on the FB. Granted we could put on the long pants, sweatshirt, and jacket, but then I might as well be sailing. The flip side of that is when it is really sunny. We have a bimini over the FB which during the right time of day provides good shade, but I don't want to sit in the sun for a couple hours so that will send me inside as well. So it isn't just inclement weather that makes me use the PH.
As others have said, the PH is a just a lot more convenient to the rest of the folks on the boat, the galley, the head, etc...
If I am going to be leaving a particularly tight dock or tricky anchorage, I do like the visibility I get from the FB. On our last trip we were wedged into a tiny space at a dock that we had to back out of with boats on all sides. Despite the drizzle, I used the FB to get us out of there because of the visibility to the stern.