Why an upgrade utility isn't included
Detractors of Linux Mint will often cite the fact that there is no official upgrade procedure to be a downside that warrants considering other distributions. In enterprise environments, system administrators surely wouldn't want to reinstall Mint on everyone's computer every 9 months, especially if it's a company that has 100 or more computers. To be fair, the lack of an official upgrade procedure is definitely an inconvenience. However, in order to understand why things are this way in Mint, one must look at the bigger picture.
First, upgrading from one operating system to another is almost never a smooth experience. To put it in perspective, with 30,000 or so packages in the repositories, there's literally no way to test how an upgrade procedure contends with every possible combination of packages that may be installed on one's system. When developing a distribution, a clean installation would be the most tested process...