You can use front-page.php to create a static front page, it will override all other templates and static front page settings, but the problem is that you can't edit the front page then.
You can't edit the front page from inside WordPress, and add content to it, like you can with pages.
If I choose to create a new page and use it as the static front page from the reading options in WordPress, I am able to edit this page.
The point of a CMS system is to make it easy to manipulate content, using front-page.php I have to edit the code directly.
So why should I use front-page.php instead of adding a page and setting it to be the static front page in reading options?