Exploiting weak identity credentials is one of the most common elements of most attacks. Even attacks that seem unrelated to users, such as recent point of sale (POS) attacks at well-known retailers like the ones you have mentioned, can be traced to insecure passwords. Often, the same password is repeated for all organizations managed by the POS vendor, and once it is stolen, it essentially becomes a default password and the attackers can gain knowledge of the customer base.