1. Cost. Upgrading software is expensive. If an upgraded licence costs $50 that may not seem like much, but doing that for 5,000 machines gets really expensive really quickly.
2. Compatibility. Very often, companies will have custom or specialized software that may not function well with newer software. If the older software doesn’t have patches/upgrades, or those patches/upgrades are not cost effective (see point 1) you may need to keep other software downgraded in order to preserve compatibility.
3. Security/Reliabilty. Older software – particularly in the enterprise – can be more secure and/or stable because the bugs and security holes have been patched. Newer software may introduce newer bugs that can compromise operations.
4. Usability. Not everyone is computer literate in a company and upgrading their software may confuse them to the point where they struggle to do their job until they learn the new software.