You want to use a framework for your new website, because you don't want to rewrite the same functionality that is needed for every website over and over again. Functionality such as showing a page based on the URL, allowing users to login, managing users, offering e-mail functionality etc. Banshee has been written with security in mind, so it's likely that if you use Banshee and stick to its simple and easy rules, that your website will be secure as wel. That's why you want to use a framework.
