I don't think that they die out because they have some specifications that no one can replace. If you want more specification, check out this blog of cakephp or zend . outsourcing4work.de/en/codeigniter-zend-yii-cake-…

Cheers :)

Well i think the community of PHP and frameworks grow fast, and today maybe the functionallity and configurations of Zend and Cake and some others frameworks it's outdaded! With Symfony on head an strong community behind the framework, and new frameworks like Laravel and Phalcon, all the options and function by the old ones become outdated. Maybe if Zend or Cake make a major version update, can come to the actually.