All UPPERCASE is easy: it was used for emphasis in written English from before computers. I'm old enough to remember platforms that had no lowercase -- Univac 1108s, for example, used a 6-bit character set and had no lowercase letters -- but those systems predated email, and weren't used for actually communicating with people except in very constrained ways. BTW, Swiss bankers don't use Helvitica. They use Fraktur.