Robert Uncle Bob Martin argues that an applications purpose should determine its architecture; its delivery mechanism should not. If you look at an architectural drawing of a church, for example, you can tell its a church. But if you look at an architectural drawing of a web application, the fact that its a web application should not be the first thing you notice.
The web is a delivery mechanism. The web is a detail. The web is not particularly important to your application. The web is a pipe. It is nothing more than a pipe. It is not the central abstraction of your application. It is not the grand, over-arching thing that makes your application the application it is. The web is just a dumb detail. And yet it dominates our code.