There are a few good reasons to use commercial themes (templates) from market-leading vendors on your WordPress and Joomla Websites. Here's my list:
- Cost effective vs custom CSS
- Endless variety of designs
- Cross-platform compatibility
- Smartphone compatibility
- Technical support / community
- Administrative features & site building tools
Cost effectivness. Custom-coded CSS entails a custom design and associated implementation. The cost to create a fully-featured template for Joomla (or theme for Wordpress) can easily exceed $10,000 at most small design shops, and multiple times that at larger firms. Contrast that with the sub-$100 cost of most commercial alternatives. Even allowing a couple of days for an art director to tailor a commercial wordpress them to support your brand, it's a no-brainer.
Design variety. New themes come on the market all the time, from top-tier commercial vendors (Rockettheme and Woothemes are great places to start), freelancers, and everything in between. There are aggregators (like themeforest.net) that provide a marketplace and feedback mechanism to help you make good choices. As I type, Themeforest boasts just under 10,000 themes and templates (for Websites, e-commerce carts and email, too). It's likely that you'll find something you can feel comfortable with, and you won't have to pay for or wait for its development.
Cross platform compatibility. These themes usually provide responsive design (viewable on smartphones and tablets out of the box), support a wide range of browsers (including back-levels of Internet Explorer), support accessibility standards, etc.
Technical support. Perhaps one of the most valuable aspects of purchasing a commercial theme is that there's usually a support mechanism in place. We tend to buy from vendors who provide ticket-based support and/or community forums where the vendor participates actively. This makes a big difference when you have a compatibility issue or implementation question. When you author your own theme, you've got none of that support - and it comes in handy.
Site building tools. Many contemporary Wordpress themes include page builder dialogs that allow you to construct a page visually, including images and text in various layout styles. This makes it much easier for non-technical admins to maintain the site independent of programmers. Some vendors also customize the "back-end" or administrative tools to further enhance the site building experience.
Open source benefits. If you construct a site via tools like Dreamweaver, you're missing out on a lot of site building tools. Joomla and Wordpress have hundreds of thousands of developers creating special-purpose software to add site functionality (e.g., event registration, image galleries, SEO, spam blocking, forms, etc.). Some of these scripts can be implemented in custom-coded sites as well, but it's just a little harder to make it all work. And if you're developing in Wordpress, you can be certain that there are legions of people who can support your site if you need help.
There are some sites that are worthy of custom-coded templates, but they're few and far between. A good web design shop will know how to tailor a commercial WordPress theme or Joomla template to make it unique to your business. IMO, the benefits of the commercial supplier's tools and support will far outweigh any negative connotation of using a template for your site. Our site is built on a commercial WordPress theme and we think it's pretty cool indeed. What about you?