This question is more for the VPS and the dedicated server users. A web control panel is likely an option when you order one of these web hostings.
The popular control panels are Plesk Onyx and cPanel with WHM. cPanel can hosts unlimited domains while Plesk Onyx comes in 3 variants support up to 10, 30 and unlimited domains. And if you are a reseller or managing a lot of users for a different domain, you should order Web Pro edition and above.
This has happened to be an option when you are ordering a VPS or dedicated server. You might be saving up to $20 every month if you are not installing a licensed control panel. There are free one but they have limited functions.
In my opinion, you can do most things without a control panel. But how soon? How fast? Who is or are using? Alright, we need to find out who are the users. If your users are business users and you are reselling, you need a control panel. If you are the administrator, you can do without in these conditions;
- Do you have the knowledge to do it? Like to create a website, mailbox or an SSL certificate.
- Do you have the resources? Like installing a mail server or an FTP server.
- Do you have the time? If you need to repeatedly do the same task frequently,
To save the money without a control panel might require you t spend more time managing websites. Unless you are confident to do it quickly and the steps are correct, otherwise a control panel makes your life easier and you can get things done quickly.