The impressionistic look of this resulted from 1) it being a pastel drawing and 2) the paper is a special sanded surface with a coarse grit. Such a surface is not amendable to fine detail which is OK if you don't want fine detail. Also the color of the sand on the paper used here was also a light brown and if you let the surface peek through, the paper itself can be part of the color scheme.
Sanded paper has become popular with pastelists because the grit holds onto the pastel better than if you use a regular paper surface. So you can layer the different pastels on top of the other without actually blending them, a practice that too often produces a muddy looking brown. But most of all and depending on the particle size, the sanded surface produces a textured drawing which some connoisseurs prefer.
The biggest drawback is that sanded paper tends to be rather expensive. The aspiring pastelist may be tempted to try experimenting with paper from the local hardware store. Certainly you can experiment, but if you make a drawing you like, you may find it begins to fall apart after a few months. Commercial sandpaper is not, alas, what we call archival quality.