It goes without saying the determinism of PRNGs can be a very useful property. But if you need that property, you if can explicitly seed it from a random source

It goes without saying the determinism of PRNGs can be a very useful property. But if you need that property, you if can explicitly seed it from a random source, you can also explicitly seed it with 1 if you wanted. The PRNG/RNG distinction you make is slightly false. Even if you're doing cryptography usually don't want to use a true source of entropy directly, you're better off feeding several sources of entropy into a PRNG. That's what both /dev/random and /dev/urandom give you (despite some common misconceptions). What most developers really want is a non-deterministic (randomly seeded) PRNG. When you actually want the PRNG to be deterministic, you usually also need to seed it explicitly anyway (e.g. having multiple runs in the same app or allowing the user to specify a seed to generate a map in a game). The implicit is useful for very few developers (if any), and confusing for the vast majority of junior developers out there.