A slightly unpleasant side effect of riding in the rain is getting a wet bum crack. You can prevent this by installing mud guards - but they are strictly for poofters. If you walk into a proper bike shop and ask for mud guards, the thin-as-rakes pro-racer staff will beat you over the head with the nearest hard object to hand (possibly a bike frame or a pump) and throw your unconscious body into the street. And they'll staple directions to the nearest bike shop for poofters to your forehead. Misunderstandings of this sort could be avoided if mud guards were produced in one colour only - pink. Then it would be quite clear who was allowed to install them.
Getting an icy cold crack wash first thing in the morning is a function of two variables. The first is the volume of water on the road. A light sprinkling of rain might make the road surface wet, but you need a critical mass of water on the road before it starts to adhere and flick off your tyres in sufficient volume to douse the hairy behind bits.
The second is speed. At low speed, your wheels won't be turning fast enough for any water that has adhered to them to flick off with any pace. Water needs to flick off vertically and travel for at least 6-8 inches if it is to fly far enough to give you a constant douche. However, at 50km/h, I produce a rooster tail tall enough to reach my neck. I could draw a graph to illustrate the interaction of road surface water volumes and velocity, but it would probably look like a couple of mud guards - and I don't want to go there.
You might think that pouring a steady stream of cold, dirty water down your crack early in the morning is about the most unpleasant thing that could happen to you on a wet day. But you'd be wrong. By far the most unpleasant thing is extracting your wet, smelly riding gear from your locker at work and climbing back into it at the end of the day. It's cold. It's clammy. It's probably spattered with mud and other unidentifiable road debris (just think of all the snot that cyclists blow out of their noses each morning...and where that ends up). It definitely reeks. It's about as pleasant as smearing your body with cold porridge.
And this is where we sort the hard men from the soft.