I still prefer wearing rain gear, but it's a personal preference. My reasoning is that it tends to be relatively cooler when it rains, so if I ride without rain gear, I'm often still going to be chilly, which I dislike. I'd rather be hot and wet than cold and wet. Again, my personal preference.

ETA: Plus, the level of wetness is different between sweating inside rain gear, and being in the rain without protection. I [hate wet shoes and socks!