And I would argue that this is by design.
I think Apple walks a fine line between ensuring their default apps provide a minimum standard of quality, and not being so good that users are completely satisfied and don't bother with third party apps at all. As a general rule of thumb, I find that the stock apps give the user roughly 80% of what they need. As it is, stock apps already benefit from native system integration (extensions, Siri, the oddball feature here and there like mail drop or Apple Pencil support for notes).
The whole idea is to push software developers to work even harder to create great apps that give people reason to want to use them over the preinstalled defaults on iOS, but not make it so hard that they give up altogether.
Imagine how frustrating it would be if Apple were to continuously sherlock key features to add to their own apps. After a point, the developer would just give up, because how do you compete with default apps that have access to APIs they themselves lack? That's not how you maintain a healthy app ecosystem.
I am talking specifically in the Apple Maps context here, and nothing more. Remember one of the possible reasons Apple went with their own Maps app? https://www.theguardian.com/technology/2012/nov/05/apple-google-maps-iphone-dropped. I don't think they were encouraging competition in this context. I agree with you though in this example in that they are giving users a certain % of what they need in a Maps app.