This WaPo article gives us an historical perspective on why the Internet was designed to operate mostly with no encryption.  The money quote:

“Back in those days, the NSA still had the ability to visit a professor and say, ‘Do not publish that paper on cryptography.’ ”
As the ’70s wound down, [Vint] Cerf and [Robert] Kahn abandoned their efforts to bake cryptography into TCP/IP, bowing to what they considered insurmountable barriers.

This is really a great piece on how the internet morphed from an academic & defense research project to the collective nervous system of humanity.  I came into the field during the second decade of the Internet and it was not really a part of my life until about four or five years in.  I really enjoyed the insight into the earlier days.  Note the role Richard Stallman took back then – it hasn’t really changed much, at its core.

h/t to Rob Slade via CISSPForum.