The two groups are as follows: Umbrella People and Rain People. At first, I was simply content with Umbrella People and No-Umbrella People, but I felt that the No- sort of distorted the idea. It's not that they are anti-umbrella, it's that they just don't normally use them. Nothing personal.
In any event, people fall into one or the other. Have you ever seen those poor souls who, when trapped in a rain storm filled with high power winds that are ripping their umbrellas every-which-a-way causing them to become drenched no matter what they do, still cling to that umbrella as if it were a magic talisman? Have you ever seen them?? That is a hard-core Umbrella Person. He will cling to that umbrella if a hurricane is pelting him with hail. He could be trapped in the movie Twister and feel safe as long his umbrella is there. There may be only 15 feet between them and their car, but they'll spend twenty minutes searching their house for an umbrella.
Then there are the Rain People. These people will walk to out into a hurricane if necessary, and to Hell with an umbrella. They recognize two universal truths. One: They are going to get wet, umbrella or no umbrella. Two: Rain will not cause a chemical reaction that will end their lives. Because of this, they have both hands free when they reach their car, and are easily able to get their key, put groceries in the car, or whatever they need to do. The hard-core Rain People have a tendency to simply stand in the rain to feel the rain, simply because they want to do so.
That is how humanity should be categorized.