Indeed. Historically these walls have been used in orchards, where they are ideal. The wall serves an important function: it buffers heat. This can make all the difference, especially in late frosts, which are doom for the bloom. Of course, the added warmth can also mean you can grow varieties in a colder climate that you normally wouldn't be able to.
Serpentine or Crinkle-Crankle walls, apparently a Dutch innovation.
> Although it's actually longer than a linear wall, a serpentine wall economizes on materials because the wall can be made strong enough with just one brick thin. The alternate convex and concave curves in the wall provide stability and help to resist lateral forces. Furthermore, the slopes give a warmer microclimate than a flat wall. This was obviously important for the Dutch, who are almost 400 km north of Paris.
> Variants of the serpentine wall had recessed and protruding parts with more angular forms. Few of these seem to have been built outside the Netherlands, with the exception of those erected by the Dutch in the eastern parts of England (two thirds of them in Suffolk county). In their own country, the Dutch built fruit walls as high up north as Groningen (53°N).
It depends how you define "wasted". If it were a flat wall, it'd give the interior more space by just pushing it out to the furthest point in the wavy wall. I guess you could say that whatever the magnitude of the wall is would be wasted.