"Joomla is an award-winning content management system (CMS), which enables you to build Web sites and powerful online applications. Many aspects, including its ease-of-use and extensibility, have made Joomla the most popular Web site software available. Best of all, Joomla is an open source solution that is freely available to everyone." - Joomla! The CMS Trusted by Millions for their Websites
If it's free and easy to manage why do you have to hire someone?
There are many reasons that will drive you to hire someone for managing, editing, building or helping you with your Joomla website, but the most common are: the server where you host your files doesn't fit well with Joomla, you may need many commponents and plugins, which conflict with each other, or you many need to add a cutom module, a custom template or design, a custom form or remove custom features that are included by default. There are also too many commercial components that cost an arm and a leg for just one website only but if it's for many sites then the costs are justified.
Joomla is a professional and useful CMS platform but this doesn't mean that every one can use it and work with it, because it takes a lot of time to learn it and work with it. SHOM Tek uses Joomla and we've loved it since 2009. It's the passion we have for our work that has made working with Joomla! very easy for us.