Anyone who knows about caching probably has WP Cache installed. If not, they should - it's an absolute God-send if you get Dugg or if you're on a poorer server with a fair number of visitors.
Either WP should develop a caching system just like WP Cache, or perhaps writing WP Cache into the software, or as a bundled plugin.
I feel many users may be on cheap-ass-hell servers in order to get their own domain but without paying more than a few pennies a year. These users are more likely to be the ones who don't give much though to server optimisation or who don't know a great deal about how MySQL works. To include a simple but powerful caching system like WP Cache would be great for users, beginner or advanced.