[bct]

> Like, why do we still use plain text in flat files for source code

Information density. Images and graphs are exceptions to the general rule that text can contain a lot more information on one page than graphics can.

[e12e]

Well... if you look at things like (colour)forth (and highlighting in IDEs/editors) -- most people don't actually code in "plain" text (there's colour/typographic hints that indicates meaning). Other than that -- we do tend to still use text to represent mathematics, so I don't think it's that strange that we usually represent code as text. For another exception to the rule: see graphical editors for UI layout, as seen in many IDEs (ie: using graphical programming for representing graphics) -- or 3d modellers like Blender (when you add bones etc, you could argue that you're "programming"). Then there's of course spread sheets -- but they tend to be pretty text-focused -- even if they use layout to great effect.