Smartphones are not phones. They are computers with functionalities comparable to that of a "real" computer.
They have the same weak points like computers, but their portable format carries additional risks (loss, theft, unsecured connections). They can also be used for malicious purposes (network spoofing, invasion of privacy, misuse of images, etc.).
Also, smartphones are very often the first point of contact for connected objects and make it possible in particular to control them or simply exchange data with them. Smartphone security is therefore essential if we want to ensure the security of the connected objects that revolve around them. Conversely, compromised connected objects could in turn infect smartphones.
Smartphones can also help us control our connected objects, and to secure them or find them in the event of a loss. In short, connected objects, smartphones and cloud services go hand in hand and we must ensure the safety of each of them to prevent problems from quickly spreading to the whole.