The loose strokes signify an approximate handling of the figure, perhaps just trying to roughly lay out a pose for this figure, but without concerning oneself too much with the actual detail to be added. This most likely would have been part of one of his sketchbooks before later being removed to become an individual piece of paper. In many examples, for this reason, there would also be another work on the reverse.
The lack of detail may also suggest that this figure's role in the final artwork is not that considerable - perhaps a part of a group of figures in the background. The likes of Durer, Bruegel and also Bosch would often add people across their scenes, normally going about their daily lives in either work or pleasure. Historians would be able to determine this figure's occupation and status society from the clothing added, even though its detail is limited.
Most of the drawings still remain from Durer's career are anatomical studies of varying levels of fidelity, ranging from the simple such as this one, to others that would have taken much longer and include much more detail. The simpler ones may have been passed around studios in order to teach others of how the master wanted certain features to be constructed.