Such surrogates are a useful, cheap way to gain insight into the global behavior of the system. Optimization can still occur as a post-processing step, although with no update procedure (see above), the optimum found cannot be validated.
Surrogate models are a cost-effective method to gain insights into the global behavior of the system. Optimization can still be performed as an afterthought, although without any update procedure (see above), the optimal solution found cannot be verified.