Adoption can be modeled to depend on ease-of-use driven by apparent need, influenced by a user's risk-appetite. But also popularity, being a differential equation, where it's rate of change is proportional to the number of users. So if the apparent benefit isn't there, most people being reactive, probably won't use something better, especially if it's as hard to get working as old Postgres... They use MySQL until Postgres demonstrates advantageousness.
As noted up-thread, the root DNS servers weren't signed until 2010.
Off-the-record messaging (pidgin-otr) is available since 2005, PGP since 1991 and the theory behind it (RSA (1977), Diffie-Hellman key exchange (1976), etc.) is much older.