Many OSes take the advantage of having a local DNS cache, like Windows and MacOS. Mostly, DNS request hardly change and they have their own Time To Live value, so re-requesting each time the IP address of a domain is pretty an unnecessary process. Setting up a DNS cache for Ubuntu Desktop (or even Ubuntu Server) by default would enhance the desktop experience, save bandwith and speed up internet. Web page rendering is deeply enhanced since a single page envolves severam requests to differente A ADDRESSES or CNAMES.

This is a pretty easy, simple, powerfull feature and already a standard in modern operating systems as mentioned before. I strongly recommend it to be implemented.