As the others have pointed out those developers are just trying to make money off you by having you host your site with them. Also, be aware that they can also lock you out of your website if you two start having a disagreement.
They also do not know what they are talking about. If you look at GoDaddy's details of their plans (http://www.godaddy.com/Hosting/Legacy.aspx?ci=8971#details) their packages do include content management systems.
The way we handle things is that we have the client register their domain name with one company, setup their hosting with another and have us to the creation of the website. Why? Because the client remains in control of their website. If they want to change domain registrars, they can (as long as they follow the registrar's rules). If they are fed up with the hosting company's poor service, they can move (again following the company's rules).
Now, as far as content management goes, please don't use the systems provided by your hosting company. Why? Because some of these are not up to date plus they may be customized for the hosting company, therefore hard to backup and move.
There are different ways to have a site set up so a client can update themselves. This depends on whether they are willing to learn some HTML and CSS so all is required is Notepad to edit the pages.
Even if you go with something like a self install copy of Wordpress and custom theme, it is to your advantage to learn some HTML and CSS so you can troubleshoot problems.
Also consider whether the developer knows how to make a search engine friendly theme/website. It takes more than meta tags, alt attributes, keywords, submitting to the search engines and link building to have a search engine friendly site. How the background coding is done is also important.
Reading through the search engine guidelines would also be time well spent as you would have an idea what techniques will benefit your site and what techniques will cause you problems.