If Microsoft hadn't burned a decade's worth of "leave auto-updates on to keep your system safe!" public goodwill by force-feeding WIN10 BS to a massive number of people who did not want it, it's highly likely that this update would have been nearly unconditionally applied.
The default attitude of most people I've interacted with regarding technology is apathy. If it works, they're happy and they leave it alone.
Do you really think that a significant number of non-tech people would have gone to the trouble of looking up how to turn off updates to their facebook/email/google machine if Microsoft hadn't caused a massive shitstorm with their forced update BS?
The vendor is entirely at fault for making stupid short-sighted decisions that caused users to lose trust in the update process. No amount of handwaving can change that fact.
- If Microsoft had coded its software properly there would be no need to patch vulnerabilites,
- If the NSA had told Microsoft about the vulnerabilities when they were discovered instead of exploiting it (Assuming the NSA did not tell MS to not patch them on purpose),
- If Microsoft did not have decades of being untrustworthy gathering the logical response of disabling auto-updates,
- If Microsoft had not paid vendors to have windows pre-installed on new computers it would have the monopolistic position it has today,
- if the NSA exploit and tools had not been made public,
- and so on...
All these are also valid ways that would have prevented wannacry spreading.
The global scale of it shows how the end user is less trustworthy than the vendor.