Do you know that even after deleting a plugin/theme from your WordPress website, some of its leftovers may remain in your database? Such as orphan options, orphan tables, and orphan cron tasks. As you may know, not all plugins/themes care about the housekeeping of your WordPress database. As long as you are removing plugins/themes, leftovers will be accumulated in your database and will influence your website performance. You should clean this unnecessary data to reduce the size of your database and improve efficiency when accessing tables. In addition, your backup files will be quicker and smaller.
Demo: https://sigmaplugin.com/downloads/wordpress-advanced-database-cleaner