Maintenance is much more practical if everything in your dependency tree uses the same version of every dependency. Achieving this in practice is much of the work distribution maintainers have to do.
Doing this has a couple of key advantages:
1. when a security vulnerability needs patching in a stable distribution release, the security team only have to patch one version instead of a dozen or more different versions bundled all over the place
2. a library that depends on dependencies A and B, both of which depend on X, can actually work properly if it needs to pass API objects created by X across between A and B, since X is of the same version
In an ecosystem where it's considered acceptable to "pin" versions of dependencies and also call any system that doesn't use the pinned versions "unsupported", both of the above two cases become impractical.
Whether you use shared libraries or static libraries, the above matters still exist.
Doing this has a couple of key advantages:
1. when a security vulnerability needs patching in a stable distribution release, the security team only have to patch one version instead of a dozen or more different versions bundled all over the place
2. a library that depends on dependencies A and B, both of which depend on X, can actually work properly if it needs to pass API objects created by X across between A and B, since X is of the same version
In an ecosystem where it's considered acceptable to "pin" versions of dependencies and also call any system that doesn't use the pinned versions "unsupported", both of the above two cases become impractical.
Whether you use shared libraries or static libraries, the above matters still exist.