If you would like all Post Types to have template selection functionality, please update to [WordPress version 4.7](https://codex.wordpress.org/Version_4.7).

**Quoted from the codex page linked above:**

> **Page Templates for Post Types Add support for post type templates.** 
>
> Add support for post type templates. By opening up the page template
> functionality to all post types, theme developers have even more
> flexibility with the WordPress template hierarchy ([read more](https://make.wordpress.org/core/2016/11/03/post-type-templates-in-4-7/)).

As far as having custom template for other areas of your WordPress website; Please refer to the following useful links:

 1. [Developers :: Theme
    Handbook](https://developer.wordpress.org/themes/) OR [Codex ::
    Theme Development](https://codex.wordpress.org/Theme_Development)
 2. [Developers :: Theme Handbook :: Theme Basics :: Template
    Files](https://developer.wordpress.org/themes/basics/template-files/)
    OR [Codex :: Templates](https://codex.wordpress.org/Templates)
 3. [Developers :: Theme Handbook :: Theme Basics :: Template
        Files :: Template Files Section](https://developer.wordpress.org/themes/template-files-section/)