One valid reason is that its cheap. mostly even free.
The other reason that it is Open.. which means that if you need to change things to better suite your needs, you can do so, contrary to Applications like SAP or Microsoft products.
Website Content Management Systems
For instance you could setup your website and have it build [...]

Want to use an alternative free Office document software package, then Open Office might just be the thing for your!

If you want to have a website for your business, please follow the Guidelines below:

Write down the things you want on your website
Decide on your domain name
Get your domain and hosting provider
Do it yourself tips and tricks
Use a good designer
Start to build the content of your website
Start to promote your website
Learn from your Statistics and mistakes

Write [...]

Building the site for Small and Medium business has started!
 Stay tuned to get information for you business with Topics in the categories:
On-line presence
Information Technology
Communication Marketing and lots more…
I hope this site will turn out to be a valid source for you, and will find it your own Personal Digital Assistent.