We normally keep a number of things inside our pockets, depending on which ones we use the most. Personally, I almost always keep a handy pen inside my pockets, because you will never know when you will need them.
You will never know when you will suddenly have the need to sign an important document. When you are a busy person, there are a lot of documents to sign and there really aren't any definite schedules for such activities.
Or, more normally, it's just that you have to write down a phone number on any sheet of paper. Unless you have sharp memory, I'm sure you already know what I am talking about.
The worst thing that could ever happen to anyone who usually carries a pen around is to have the pen ink spilled inside your pants. You'll be just surprised one day when, once you reach inside your pocket, you find pen ink scattered all over your pants, your hands, and probably your shirt. Pen ink is difficult to remove, so you might as well throw that away.
You don't have to experience that, not when earning the money you will use to replace the shirt is difficult. We have here at Office1000 some plastic pocket protectors where you can put your pens inside. Now you don't have to worry if the ink spills. It all stays in the pocket protector.