My best guess is it has something to do with proprietary hooks that Google has placed in Earth and Chrome — all the better to track and gather information about the user.
Only Google can really answer this question, as Apple does not participate in the Google product development process, and it is Google's responsibility to make Earth compatible with Safari — if they choose to do so.
This is a user-to-user support community, so Apple leadership and product development teams are not going to answer here from an Apple perspective.