Just to add to this: Apart from the security aspect of hosting your software dependencies internally, it also gives you the added benefit of better availability and performance.
As you mentioned in your other comment however, this presumes a certain mindset in people where they are willing to plan upfront and are mindful of the dependencies their software needs. As you say, just pulling whatever from Docker hub is certainly easier.
Internally hosted repositories also allow you to pull and install updates at your own pace, possibly days after they have been released upstream. So if a patch is borked you won't be affected.
As you mentioned in your other comment however, this presumes a certain mindset in people where they are willing to plan upfront and are mindful of the dependencies their software needs. As you say, just pulling whatever from Docker hub is certainly easier.
Internally hosted repositories also allow you to pull and install updates at your own pace, possibly days after they have been released upstream. So if a patch is borked you won't be affected.