The softaculous_backups folder in /home/$username/softaculous_backups contains files that the user has created from wordpress manager backup using the cpanel. If your users don't clean it up, it can start consuming a lot of disk space on your server.
If you want to clear the softaculous_backups folder of all users, just run this command.
find /home/*/softaculous_backups/* -exec rm -rf {} \;