I have had experience from both sides of WordPress.
Being first introduced to it as a site owner and then as a developer.
Being given the reigns of your site to upload and change at will is thoroughly liberating and gives you a sense of accomplishment and breaks your dependence on others to help keep your content and images updated and fresh. Unless something drastic happens and you happen to break things really badly you can say goodbye to your developer/designer and take over yourself.
No more costs incurred.
From the developers side of things WordPress is a great environment to work within if you know how to tweak themes more to suit your clients needs.
For me, it’s a playground.
Many developers are horrified and look down on those of us that love and use WordPress and while a custom site is great and your limitations are only dependent on how much you know I still find WordPress thoroughly enjoyable – maybe because I am such a css enthusiast.
I have been scolded on a few occasions for my indiscriminate use of css.
Luckily I do not give much credence to what others think of me and my practices, likes and dislikes and use WordPress happily and enthusiastically.