Opening Provider-Hosted App Page in the modal dialog.

I'm new to app development in SharePoint and I'm confused by what the limitations are when opening a page that resides inside the app web in a modal dialog.

Why will SharePoint allow me to open in a modal dialog AND navigate between .ASPX pages that are inside my web project but not between MVC Views?

Let's say I create a custom action and define the url by something like this:

~remoteAppUrl/MyController/MyAction?{StandardTokens}&SPListItemId={SelectedItemId}&SPListId={SelectedListId}

What will happen in my case is SharePoint WILL open MyController/MyAction but as soon as I try to go a different view I get the following error:

"This content cannot be displayed in a frame
To help protect the security of information you enter into this website, the publisher of this content does not allow it to be displayed in a frame."

On contrast if I point to an aspx page I'm free to navigate among them, why is that?

Thanks in advance