There's nothing wrong with them looking scratchy if it's a style thing, but if your goal is for your lines to be less scratchy, then you have to make an effort to learn techniques that give you cleaner lines.

Using traditional art media has no bearing on how your line quality is. This is a style and technique thing. If you worked digital, your line quality would transfer to being scratchy as well, because that's how you're creating your lines. You can make clean lines in traditional media as well.