Not really - though several such things can be easily installed for your clients’ use.
Absolutely! Most any such tool can be installed (thinking cmsimple.dk here, for example).
People are using a little bit of everything here, though with the “one-click” install of Joomla! and WordPRess ther are many users here taking that “easier road”.
I know that Joomla! can be a bit of an overkill for simpler sites, but the recent versions of WordPress, with the fairly recently added “Pages” functionality, makes a very serviceable and easy to use solution for what you are describing.
I think it is even easier to use than the “site builders” you refer too, and with the ginormous number of templates available, a user can put together a very attractive site in almost no time.
You might find that if you look more closely at using WordPress as a CMS/Sitebuilder instead of just as a blogging tool, you will find it meets your clients’ needs very well.
Other “simpler” CMS type systems that I have used at DreamHost with success include cmsimple (already mentioned) and websitebaker, There is also a pretty good selection of such things you can actually test “in the wild” at opensourcecms.com (look particularly at the “lite” section!).