A hacker can easily replace your shared library with their own malicious version or intercept calls into one as needed. As the number of distinct binary blobs for an application increases, the surface area for attack vectors increases making security a nightmare. Every piece also needs to be individually signed and authenticated adding more complexity to the application deployment.

As the gp mentioned, Static libraries have a lot of advantages by having only one binary to sign, authenticate and lockdown/test/prove the public interface. The idea is extended into the "Unikernel" approach where even the OS becomes part of the single binary which is then deployed to bare-metal (embedded systems) or a Hypervisor.