People I know with computers who never do the updates get into a scramble to keep their computers working when updates are forced or their systems just start to malfunction. Software continues to be developed over time. Your hardware is a static object. It stays the same throughout the life of your computer. However, the firmware that runs hardware can need updating. It is programmed onto a flashable chip. That can bring new life to hardware. If you do not update, you can get an error code 0x80244019 when updating Windows or many other error codes. If you have not done any updates, you cannot just jump to the latest update in some instances.
For example, if you have not updated to service pack 2 on an old version of Windows, it is unlikely you can just go ahead and jump to service pack 3. Of course you do have to realize that Windows is on version 10 as of this writing. The old operating systems get to a point they are no longer updated for security threats or vulnerabilities or drivers and bug fixes. Your legacy product may no longer be supported. You may think that since the computer is still working okay that there is nothing to worry about. That is not true.
Your computer may be vulnerable to hacks and other threats by not installing updates. If you have even one thing that is personal information on your computer, it may be compromised. Even if you do not do banking or anything on an old computer, it may be a gateway to other computers on your home Wi-Fi network that you do have personal info on. You really cannot be too careful. Do the updates for as long as a product is supported, and then recycle it when the operating system is no longer going to be updated.