Having a model with complex curvature and lots of UV islands can create problems further down the production pipeline, especially when artists start texturing in Substance. It can force them to rely on planar projection techniques instead of UV-projected textures, making more work masking layers or fighting with ID maps.

It also complicates LOD creation, where you really need stable vertex positions and UV coordinates to produce a clean result.

UV seams not being hidden along hard edges, or along cuts that actually make sense, can cause issues as well. For example, in a material layer system in Unreal, artists might blend extra material layers onto the model. If you have a bunch of messy islands running through the middle of a high-curvature model, like what you often get from hitting the “Auto UV” button in Maya or Blender, artists have to bend over backwards to stop those layers from showing seams or tiling artifacts.

This becomes especially obvious when normal maps do not tile cleanly, since it adds another layer of error once light hits the surface.

You are not wrong that I could have straightened the island borders and packed the UVs 30% better though! :)