The point that rand() detractors are trying to make, is that rand() is also bad for non-cryptographic purposes as well. Its badness vary with the implementation

The point that rand() detractors are trying to make, is that rand() is also bad for non-cryptographic purposes as well. Its badness vary with the implementation, but with the implicit seeding, thread-safety issues and bad distribution on many implementations it should be generally avoided for all usage scenarios that want random numbers. If you don't really want random numbers, but just "some numbers, I don't care if they're random or not", rand() is fine, but using "int myNumber = 42" is faster and safer.