> One possible reason is that pre-baked primes can be designed to avoid certain pitfalls (e.g. primes close to powers of 2, which the article implies can be solved using the much faster algorithm) or otherwise to be resistant against certain cryptographic attacks.

Why can't those primes be calculated on the fly? Checking a number for being within a certain distance of a power of two is well within the programming capability of a freshman CS student.

> I don't know enough about DH to know if that's really the case here or if it's merely done to avoid having to compute fresh large primes, but I'm going to guess there's a good reason for it.

Given the incentives involved, I see strong reason to believe this is not the case.