I think it is better to add

them, no matter whether you are NIW or not. First, they are important dodocuments any way which can show that you are already a concrete part of the society already. Second, sometimes some center directors reqiure them, even for cases which might not need them. So it should be wise to prepare them to avoid any possible delays. Especially for cases involving I-864s for dependents which specifically require them, an extra copy is more than worthwhile.