It was because Schulz had essential tremor. As a result, his hand shaked a lot. Therefore, he drew strips with less panels. because they were easier to draw.
In Schulz’s words, “Charlie Brown must be the one who suffers, because he’s a caricature of the average person. Most of us are much more acquainted with losing than winning. Winning is great, but it isn’t funny”
Now that’s just ridiculous