I don’t agree with your view on the prepare for the rain part.
I always have been a avid commuter rider, I have been riding scooters daily since I’m a teen. I used to store my rain wear in the trunk.
Last year I passed my licence and bought my first real motorbike (I had a dirtbike but doesn’t count as a motorbike), and I totally change my philosophy, I bought a good waterproof all-season equipment and I’m dryer than when i was using my occasionnal rainwear. At least with my new stuff, I have extra armor.