There are several reasons why Drupal 9 is great for multilingual websites:

1. Built-in Multilingual Support: Drupal 9 has built-in support for multiple languages, so you don't need to install any additional modules or extensions. You can simply enable the multilingual functionality and start adding languages to your website.

2. Translation Management: Drupal 9 has a powerful translation management system that allows you to easily translate your website's content into multiple languages. This includes both static content, like pages and articles, as well as dynamic content, like forms and user profiles.

3. Language Switcher: Drupal 9 includes a language switcher block that allows visitors to easily switch between languages on your website. This can be placed in the header, footer, or any other block region on your website.

4. SEO-Friendly URLs: Drupal 9 supports SEO-friendly URLs for multilingual websites, so you can have separate URLs for each language version of your website. This helps improve your website's visibility in search engines and makes it easier for users to find the content they are looking for.

5. User Experience: Drupal 9's multilingual features improve the user experience by making it easier for visitors to navigate and find content in their preferred language. This can help increase engagement and drive more traffic to your website.