If you only have one eye, you don’t have depth perception. If you’re able to look at things with one eye in the 21st century and the other eye in the 20th century (or possibly even the late-19th), it provides a kind of perspective that otherwise wouldn’t be available.
William Gibson expanding on: “This perpetual toggling between nothing being new, under the sun, and everything having very recently changed, absolutely, is perhaps the central driving tension of my work."
Wandering Wandering Star 