Web Development is one thing big sites can't go without. Web development is absolutely necessary to keep up with the time and add some flavor and new functions to a site, whether it'd be improving functionality of the site or adding a revenue model.
How your website develops is due to this factor of how much development it gets, will it crash under heavy traffic? or does it have a way through? Optimizing your site for best functionality, availability and accessibility all comes under this category of web development.
Those who plan to improve their site must go through Web Development.