I have to agree with you. As someone who’s just starting out with sketching, Sketchbook pro is a nice tool. I start my drawing with pencil on paper. From looking at the sketch, I can sort of feel where I went wrong but sketching proper line work as an overlay I can clearly see where I went wrong. For example for my last set of sketches, I realized that my idea of perspective isn’t too bad but my lines aren’t straight enough so everything looks off as the sketch progresses. It would be hard to get this kind of information without the tools. It’s also quite motivating to end up with a corrected version of your drawing.