Make your web application run faster
It is easy to develop your own ASP.NET web application. But making it do some useful things for your users while keeping the design simple and elegant is not so easy. If you are lucky, your web application will be used by more than a handful of users, in that case, performance can become important. For some of the web applications I worked on, performance is vital: the company will lose money if users got frustrated with the slow response.
There are many factors that can result in bad performance, the number of users is just one of them. As a developer in a big corporation, you usually don't have a chance to mess with real production servers. However, I think it is very helpful for developers to take a look at the servers that are hosting their applications.