Keeping everything up to date is great...up until it breaks something your business needs.  Internet Explorer upgrades are notorious for breaking production applications, and as such, most businesses need to test each version before allowing it to deploy in production.  When you have a dozen systems, it is easy enough to just walk to them and hide the upgrade, and uncheck the little "Install new versions automatically' checkbox; when you manage hundreds or thousands of machines, however, that task quickly moves from time consuming to impossible.