The other story here is incremental growth of camera technology. The daguerreotype came out after his voyage on the HMS Beagle, by the time Origin of Specices was published (with no photography) Cameras still had to many practical limitations to justify a worse image. By 1872 Darwin would publish a book full of photography despite his remarkable drawing skills.

Something gives me the feeling that a lot of people are going to follow Darwin's example in the near future