The increased productivity of writing in a scripting language typically outweighs the cost of extra servers. Whereas with a desktop application, you only have X

The increased productivity of writing in a scripting language typically outweighs the cost of extra servers. Whereas with a desktop application, you only have X resources to allocate to a task, you can always "just throw more servers at" a web application to some degree. It is done occasionally though; last I heard, large portions of Amazon.com were written in C.