There are several reasons why you might want to put your WordPress site into maintenance mode. Here are a few:

1. Updating Content or Design: If you’re making significant changes to your website’s content or design, you may not want visitors to see the site mid-transition. In maintenance mode, you can work on your website without visitors seeing the changes until they’re complete.
2. Testing Features: When you’re testing new features, plugins, or themes, it’s better to put your site into maintenance mode. This prevents potential compatibility issues or errors from impacting your users’ experience.
3. Updating WordPress or Plugins: WordPress, theme, and plugin updates can sometimes cause temporary issues or even break the site. To ensure visitors don’t see any potential errors during the update process, you can use maintenance mode.
4. Troubleshooting: If your website is experiencing problems, you can put it into maintenance mode while you troubleshoot and fix the issues. This way, users won’t see error messages or broken features.
5. Website Migration: If you’re moving your site to a new server or changing your domain name, you might put your site in maintenance mode to prevent any changes from being made during the transfer.
6. Site Launch or Rebranding: If you’re preparing to launch a new site or rebrand your current one, you may want to use maintenance mode to build anticipation and ensure everything is perfect before the big reveal.

Remember, the idea behind maintenance mode is to offer a better user experience by not letting visitors see the work in progress or any potential errors that might occur during an update or while troubleshooting. Instead, they see a friendly message explaining that your site is temporarily unavailable due to maintenance.

Here are 10 plugins you can use to put your WordPress site into maintenance mode:

1. WP Maintenance Mode: This popular free plugin allows you to add a maintenance page to your blog that lets visitors know your blog is down for maintenance. It includes features like countdown timer, progress bar, and a contact form.
2. Coming Soon & Maintenance Mode by SeedProd: This plugin is great for both coming soon and maintenance mode scenarios. It is user-friendly, responsive, and has many customizing options including background images and color schemes.
3. Under Construction / Maintenance Mode from Acurax: A highly customizable and feature-packed plugin that offers a variety of pre-made themes for maintenance mode, a countdown timer, and social media icons.
4. Minimal Coming Soon & Maintenance Mode: This plugin provides a wide range of design options while remaining user-friendly. It integrates with MailChimp, which is useful for collecting emails from visitors while your site is under maintenance.
5. Elementor: While not exclusively a maintenance mode plugin, Elementor allows you to create maintenance mode pages. If you are already using Elementor for your page designs, this feature might come in handy.
6. Coming Soon Page & Maintenance Mode: A simple plugin that offers basic customization options for your maintenance mode page, such as color and text options. It also includes SEO options to help your website retain its ranking during downtime.
7. CMP – Coming Soon & Maintenance Plugin by NiteoThemes: This is another option that is both easy to use and customizable. It supports custom CSS, has a variety of themes, and allows for email subscription collection.
8. Maintenance Mode by Lukas Juhas: This is a very simple and straightforward maintenance mode plugin that allows you to activate maintenance mode with a single click. It is great for those who do not need many customization options.
9. Fancy Coming Soon & Maintenance Mode by Dazzlersoft: This plugin offers a sleek and modern design, along with customization options and a countdown timer. It also allows for email subscription collection.

Remember, always back up your website before installing new plugins, and make sure they are compatible with your version of WordPress. Also, ensure to check their last update and reviews to guarantee that they’re reliable and still actively maintained.