Fear is one solution...
I once had an hour free while passing through central Birmingham, and was browsing in the local PC World. Not that I buy there, I was just checking out the laptop market. It was around the time of the release of Vista.
An assistant made a half-hearted effort to sell me something, and I made a half-hearted effort to sound interested. But then I told them that yes, the laptops were all very nice, but I had heard terrible things about Vista, and I mused it would be ideal if they could instead sell laptops with no operating system on them at all.
I knew it was pointless to say such a thing, although I wasn’t deliberately trying to waste their time – I do make genuine purchases (three separate computers since then) from manufacturers who don’t bundle Windows.
“No, we can’t do that,” replied the assistant. “That would be ILLEGAL.”
It seemed the assistant was accidentally mixing up the idea of civil legal liability (in terms of the agreements that manufacturers have with Microsoft), with that of criminal liability. But as a sales tactic, it seems solid gold…