One other reason i can think of, a pencil has a near zero chance of leaving smudges on paper or marks on your hands/clothing. Also, a better choice if you are writing on both sides of the paper and it isn't super thick, because pencil writing won't be visible on the other side of the paper.

Pencil smudges are definitely still a huge issue for left handers....

I think that pencils are of course nice cuz you can write things lightly and then erase stuff. But honestly, after being forced to use a pen when moving to Europe in HS after years of "you have to use a pencil for math".... just scratching things out works so well.

Pencils also are pressure sensitive, if you want to do anything like gradients...

I still like pencils for doing paper puzzles or the like, just cuz it's a bit easier to "fix" stuff, but it's definitely the minority of my usage.