1. Old software becomes less useful over time. This applies to anything that talks to outside systems. There's a new version of HTTP coming out, there are new v

1. Old software becomes less useful over time. This applies to anything that talks to outside systems. There's a new version of HTTP coming out, there are new versions of HTML and CSS, there are new formats for office documents, there are security fixes to SSL libraries, etc. 2. Newer applications tend to not be installable on older OSes. For example, newer IE won't run on Windows XP. 3. Therefore, older OSes become useless after a while, if you're talking to the outside world. 4. Therefore, being able to install a new OS on your hardware, can make that hardware useful longer. 5. Newer OSes may not always support older hardware. Also, companies that produce OSes (Microsoft, Apple, Red Hat, etc) may go out of business. 6. Therefore, being able to choose from a wider variety of OSes to install, increases the chances that you'll be able to find one that you can use. 7. Therefore, having more choice in OSes makes your hardware likely to be useful longer.