From the start of web site development as a profession, in say 1995, we have been in an expansion of web development software tools and techniques. What do I mean?
When it became obvious that every company needed a web site, the development industry exploded with jobs. The industry was so immature that everyone entering the industry picked up a number of different technologies to use, all of which could be used to build web sites.
For example, in languages, we have Java, PHP, Ruby on Rails, Python, C++, Scala, and asp.net. If I'm just starting out in learning to be a web developer, which one do I choose to learn?
The industry split between Microsoft tools, and open source tools. The split usually went along the lines, if the company you worked for was willing to buy the Microsoft and Adobe tools, you became a Microsoft engineer. If not, or like me you learned it on your own, you went open source.
Open source had the most expansion, just because it was open source, everyone was developing a better mousetrap to aid in web development. We learned from each other. We built all sorts of tools that competed for the developer's toolbox. The biggest question was what tools should I invest my time to learn? You didn't want to spend a couple of months learning a technology that would not be around in a couple of years.
Gradually, developers through word of mouth, forums, conferences, and blogs started to choose. And as they did some tools started to subside, and other's rose. As a PHP developer, I'm biased in that direction. So with apologies, to Java, Ruby, and Python and other languages, and in the interest of brevity, I'll look at this from that perspective.
There are still some areas that are fighting it out for dominance.
PHP Frameworks are in a shake out, but we're beginning to see a condensing here also. From some 180 frameworks, We're down to a shorter list now: Zend2, Symfony2, Phalcon, Fuel, Yii, CodeIgniter, Kohana, and Laravel, but I expect this list will get shorter, and Phalcon is relatively new. It seems like each of these frameworks has their 15 minutes of fame, until a new framework comes along, that's "better or faster." Frameworks are a perfect example of developers trying to build better and better tools.
Then we have Content Management Systems, with the top 3 being: WordPress, Drupal, and Joomla. WordPress has by far built the largest number of sites of the three.