Nikon and Canon's pro SLR ranges are product ecosystems with massive switching costs. They maintain all sorts of products and services that don't make economic sense in isolation, but are necessary to maintain a comprehensive product ecosystem. A professional or serious amateur might own tens of thousands of dollars worth of camera bodies, lenses and accessories; for a small but meaningful proportion of those customers, the continued availability of the F6 will be the key factor in their choice of camera system.

It's quite mechanically and electronically simple, though, by modern standards.