Partly because it looks pleasant, and partly because it “became” part of cinema’s visual language (photography too). The way that light interacts with the film

Partly because it looks pleasant, and partly because it “became” part of cinema’s visual language (photography too). The way that light interacts with the film is something that people have positive associations with, and they want to keep and use that look. The reasons are varied but just because the technology has improved doesn’t mean that the old way didn’t function better in certain ways (and, outside of purists who really just want to use it, film still has a place in larger formats which either don’t exist in a comparable digital form or are way too cost prohibitive). One note: I think you’re reading something that the creators did not intend. When they say “based on empirical data” what they’re referring to is the way that a specific color would look at a specific intensity based on how films actually do.