Imagine if your Drupal site has more than 30-50 modules and you wanted to update them all or you want clear all Drupal cache. If you do it manually just by unzipping and run update.php or just click the clear cache it may takes more time. Hence if you can do this all process in one single command it will be easier for a developer. Here we can use drush commands to do all work with a single command and in few seconds.