Re: We don't know the same people
the upgrade went reasonably smoothly
There in lies a risky assumption! A lot depends upon the particular machine, the hardware it contains and which security software and printer drives are installed. I expect many users simply okay the update with little thought for things going wrong... so yes it is wonderful that many do update with few problems, but for those that fail recovery isn't always straight-forward.
I have had to repair systems with failed updates mainly because: the user got bored with waiting on a system that seemed to be doing nothing, the user was in the middle of work and tried to kill the MS malware that was taking over their machine, the update failed and failed to rollback.
I've had updates go smoothly mainly because I was able to prepare the machine (eg. uninstall printer drivers and security software) and simply leave it alone for the hours it needed to sort itself out.
Personally, I now install GWX Control Panel and point out that Win7 & 8.1 will be supported until 2020 (GWX Control Panel doesn't disable critical updates) and that they are likely to be replacing their current system(s) before then; so if they want we can arrange a convenient time for a Win10 install.