My experience too is that users just carry on blithely using the PC, however slow and awful it gets. Until their friend who can deal this thing is round, then ask for help.
In my Mum's case, she's a little more cunning. She invites me over for dinner. Then after we've eaten, she turns Eastenders on - and says, "I've got a bit of a problem with my computer..." At this point, I'm so eager to get as far away from the telly as possible, that I run to fix it.
Just found a weird bug on a laptop yesterday, where Windows Update decided that it was still October 27th, so has no done any updates since that day. I'm sure I'd notice not having had the computer update itself for that length of time, but nope. A whole bunch of new icons having been installed over the years by programs so the user couldn't find his preferred ones didn't seem to worry him either. Rather than just right clicking to get rid of them - he just found stuff some other way. Ten minutes of clickety-click and 2 hours of updates and reboots later - it's now back to how it was set up.
Just things like telling the system tray how many icons it can show seems to be beyond most people. Given that I've seen this sometimes taking up half a 22" widescreen monitor...
Biting the hand that feeds IT
