It’s a usability trade off in some ways. Some people will find it confusing that a link opens their web browser. They might ask how to go back to Google Maps. This way there’s a balance. They can quickly preview the link, and if they want to keep it, they can open it intentionally in their browser or share/copy the link with one tap. Users who don’t understand how tabs work won’t find their browsing interrupted by every webpage an app throws their way.

But indeed, that doesn’t prevent an app maker such as Google Maps from making it a preference. Technically if Apple made it a preference it might break the expected UI for apps using the control. And as I noted before, there are advantages to previewing links this way, it encourages users to stay within the app.

There is no technical reason why it doesn’t log history events when loaded. It could send a message to the default browser or keep a log in the background and let the browser know when it next launches, and arguably for consistency Apple should design such a feature.

> They might ask how to go back to Google Maps. This way there’s a balance.

In iOS when an app opens another app, there is a back button specifically to go back to the original app. It's right there at the top left where the standard back button for most app navigation normally is.

> it encourages users to stay within the app.

This is one of the main reasons why they do it in my opinion. Another reason is because they can track your activity in the embedded webview.