>Only for small sites with no dynamic content.

That's a misconception. A site doesn't have to be 100% static to benefit from proper caching. For instance, say you have some information that updates hourly. Do you follow the dmpk2k strategy of saying that caching is a waste of time and hit the system every request, or do you follow a sensible strategy of properly setting the cache parameters so that caches know to keep their own copy for the correct period of time?