As an administrator, you might try new extensions for trying new functionalities. However, it is not recommended to try new extensions without knowing. As extension provides facilities, it can also be the reason for vulnerabilities for your Joomla security.
By using these vulnerabilities, your site can be easily SQL injected by a hacker. Removing unnecessary extensions is important. The fewer extensions you have installed, the faster your site will load.
Joomla is an open-source, and as an Administrator, you install many extensions to try out new functionality. It’s good to try and improve but bad without knowing the developer you install a extension. Delete extensions, which you are not going to use.