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Personally, inhouse is pretty much the only way I do it anymore. Or I'm hosted on a box that I know and trust. I'm usually the admin anyway in exchange for web space and bandwidth. Good trade for me and the box owner that way.
I thought Cpanel and the like was OS and available to anyone? I haven't used it except to get a few people out of a jam. There are a slew of GUIs for admin but they also do a lot more than web hosting accounts.
It isn't really a gap but other things: stand alone boxes aren't typically hosting thousands of nameless accounts, and that when you know how, GUIs just get in the way and limiting.
By the time you design one from scratch you can learn how to mix and match manual methods and do it faster. SSH, SFTP, and a remote text editor is enough for most things.
Suggest having someone with enough knowhow to get it set-up and secure and leave you with enough control (as a non root user) to do whatever you want easily.
There are a lot of admin tools out there and maybe some CPanel like thingies. On a local or VPN accessible server you can get it set-up and maintain it pretty comfortably.