A good many commentators here seem to work in large businesses, or even medium-sized businesses that are able to run specialised IT departments or market to such businesses.
For smaller businesses, and even some middle-sized businesses, this would be an inconceivable luxury. In such businesses the "IT guy", even if there is one, might be doing the job part time. He might simply be an application specialist. He might even be the business owner running routine backups along with all his other tasks (had this as a client). This is life in a large number of businesses. Just because the big-business-only group haven't experienced it they would be wrong to assume it doesn't happen.
For such businesses PCs are simply tools for staff to do their jobs, just as typewriters were in their day. They may be buying them one at a time as they need them so "enterprise" discounts don't apply, even if the eventual totals might suggest otherwise. In some instances they (and larger businesses) may be buying the PC and its operating system as an integral component of some larger bundle where specialist software is tied to the OS*. They may be buying a mixture of Windows and Macs for different purposes.
They have paid good money for such tools, just as they did for typewriters, just as they do for office furniture. As such they should be entitled to expect those tools to just get on with being used and not have minds of their own. If maintenance is required it should be able to fit the users' schedule and not the vendors. Nobody would, for example, expect the manufacturer to flag down a company car in the middle of a journey because an oil-filter change was due.
If the vendor that supplied those tools can't get them to work that way it's the vendor, that has failed and not the customer. And a vendor that not only fails in this way but is so arrogant as to continue blaming the customer is one that shouldn't expect to survive.
*I've seen this in a business which had its own large IT department. Processors were embedded in industrial printers and enveloping lines and their maintenance was outside the scope of the IT department. (For the enveloping lines, IIRC, the take-it-or-leave-it choice was a real-time Unix variant.) Similar considerations apply to laboratory equipment, scanners etc in the medical world and, no doubt to all manner of process control equipment.