There are several reasons why you should use template overrides in Joomla, especially when you are using any of the default templates:

1. Separation of customizations: By using template overrides, you can make changes to your website's layout and design without modifying the core Joomla templates. This separation of customizations makes it easier to upgrade Joomla in the future without losing your changes.

2. Easier maintenance: By keeping customizations separate from the core Joomla templates, it is easier to maintain and troubleshoot issues with your website.

3. Better organization: Template overrides allow you to organize your customizations in a structured way, making it easier to find and edit specific files.

4. Better performance: Using template overrides to make changes to your website's layout and design can improve the website's performance by reducing the number of files that need to be loaded when a page is requested.

5. Flexibility: Template overrides give you a lot of flexibility to make changes to your website's layout and design, allowing you to create a unique look and feel for your website.

6. Future proofing: By using template overrides, you will not lose your customizations when the core Joomla templates are updated.