Cuz--for me--I'm much more worried about locking up the front and/or having it slide. We're all generally such heavy users of the front brake, it's hard to tell how much less traction there is in the rain. Also, I've found that when it's wet, the traction can vary as you travel in a line (especially in the city where there are paint marking and oil spots). So what can feel like a safe amount of front brake one moment can lead to lock-up the next. Besides, making a mistake with the front has generally has more dire consequences than the rear.
In normal weather, I'll use the front brake (or extra lean) to adjust speed or respond to something sudden. In rain/wet, I'll drag the rear a bit going into turns or if I need to stand it up in a turn. One thing I've done to deal with the binary nature of Ducati rear brakes is totally ghetto, but works. I bleed a little bit of air into the line. It's hard to get the right amount of air, but once I've got it where I like it, it helps soften the brake application.
The discussion may be a bit academic, cuz if you shouldn't be riding so aggressively in the rain that you need to brake so hard that you'd lock up something. But shit happens.
P.S. Kiyo is a bad ass.
