Shading exercises are the a warm up, a practice that develops skill, strength, and technique.
Much like the athlete running laps, or the ballerina practicing at the bar, the mindful repetition of precision add the the larger skill.
This sketchbook page is not particularly demonstrative of anything but the practice. The shadings I did are standard shapes and light directions, but remembering the effect of shading and light on simple objects can help on a larger piece. Breaking it down, with only shades of grey, the power of suggestion with one medium, pencil, is powerful. As simple as it is, the attention to what is put on the page means something. Critically, the 4th square, the cone from above, needs to be reworked. The power in a sketchbook is the ability to leave it undone, to recognize strengths and errors, and let them be. There is a freedom in having a place to explore, and not have the results matter.