The samples should not be destroyed because they are an important source of data to understand better smallpox and many other infectious diseases. There are three main goals in studying smallpox even if the disease is eradicated in many areas:
1. As we don't know if the disease might spread again at some point, and there still a few places in which it occurs, finding better antiviral drugs to fight agains smallpox is still important.
2. The samples are important because they are studied to make better vaccines, in order to maintain the disease eradicated it is important that the population is vaccinated against it.
3. Studying this samples also helps finding improved ways of testing to detect the virus, so if and when it appear again we can take immediate action and don't let it spread again.
So, studying smallpox is important so we can keep the disease away from us, and also to better understand other similar infectious diseases.