I'm always surprised by how people can be scared into using this service.
Sadly, not everybody has a good working knowledge of computers, and don't have enough street-smarts to spot the clues of a scam.
Lots of older people who really don't know much about their computer, and are completely unaware this is an ongoing scam fall prey to it. They just think it's a nice person offering to solve a problem for them.
It's like any other form of spam or scam ... you only need a very small percentage of people to fall for it to be profitable. Especially since when you answer the phone it takes a few seconds for the auto-dialer to connect you with the guy on the other end. Because they're not calling you, a computer calls a zillion numbers, and then connects people who answer to the next available scammer.
So, if you know some older people who have computers, sit down with them and explain that the world (including the internet and the telephone) is full of lying, greedy bastards who are out to get you. It's like "stranger danger", but for adults.
Not everybody is as cynical and paranoid as people who work in IT. But you need to get them enough of both to not be victims.
I am continuously grateful that when my parents decided to get a computer I sat them down and had "the talk" (*) ... because they subsequently became people who could spot a scam on the phone from a mile away, and learned the kinds of things not to do on their computer.
(*) OK, I had to discretely have a separate talk with my father lest the lure of b00b1es caused him additional computer/wife problems. ;-)