Imagine you gave a 6-year-old, a blue ballpoint pen, and notebook at the Kingdom Hall or convention venue. Within a few minutes, they might have more stripes on the back of the seat than a Siberian tiger! (and hopefully not on their face).
Learning to write with pencils and, in particular, old-fashioned wooden pencils (not mechanical pencils) is easier. That's because of the feedback from the friction with paper... you know... that sweet wooden pencil scrubbing sound... ahh! Furthermore, whereas kids are more likely to damage pens, a wooden pencil is almost non-destructible. In fact..., you can break it in half and make two pencils out of one. So it makes total sense for kids to use pencils.