As I briefly mentioned, there are a number of reasons that you would convert your website from a single blog to a multi-site website.
It’s a great way to allow teams and/or employees from your company to have their own blogs but have them as part of the same company domain. You can use it to give people distinct platforms to work on away from the main blog on your site that can be for official news.
It also comes with the added benefit of being centrally controlled by a Super Admin user and allows you to share themes and plugins across a number of blogs.
Alternatively, you can convert your website into something like WordPress.com for your users, allowing them complete individuality while also keeping a tight hold of the system security and management.
The joy of using multi-site is that each site you create can be completely distinct without having to go through the trouble of installing WordPress multiple times or adding multiple databases. That, in a nutshell, is the key selling point.