Re: Why does illustration look like illustration?
Illustrations are generally used to clarify information visually or describe a story. The purpose of the illustration is one of the more important elements, then we arrange the illustration to convey that purpose clearly.
In the example of the the lighthouse, we have an idea of a place, but it does not convey why we are looking at it. Compare this to the city, which is trying to clarify the size, time of day, scale of some of the surrounding area. The tea set is giving us information that it is hot and set for two (we see the steam and can count the cups). Arrietty’s conversation with her mother is almost overloading us on information about the household and other things, but because there are people in the illustration we are drawn to them and what appears to be a conversation between them (Arrietty’s mouth is open, but the rest of her body isn’t poised to eat or sing).
The only information we get clarified in your lighthouse is that it is a lighthouse, and that the day may be overcast (little separation of light and shadow little bounced light, few cast shadows). It doesn’t seem to clarify why we are there or give us a reason for looking at it. If we have some text to go with it, recording the location and other elements though, it easily could become an illustration to clarify what the lighthouse looks liked at the time.
Purpose of illustrations is one of the major elements in their making. In this respect it overlaps with a bit with Fine Art very often, where a fine art painting may be trying to convey an entire story or illustrate very specific information clearly. The difference tends to be that often fine art will ask the viewer a question or ask them to interpret some meaning. Illustrations are usually combined with some kind of text to provide us an anchor to the visual information presented us.