It IS ridiculous. But people have been TOLD that AV is too complicated for their simple little minds, and too many of them seem to have accepted this statement uncritically. It breaks my heart.
Unless it's something they care about (and not everyone cares about voting reform!), being told "Don't worry about it, it's too hard to explain" is often met with "Oh, okay."
The trick is to get people to care about it so they become curious and reject the assertions of "it's too hard". The Yes campaign attempted this initially but did a poor job, in this case it turns out much easier to explain the thing than to pose half-truth arguments why people should care!
Ultimately I suspect everyone knows that "it's too complicated" is a fake argument. The real reason that Tories don't want PR is that it will spell an end to proper Tory governments. Meanwhile, the real reason that Labour doesn't want PR is that it will spell an end to proper Labour governments. The only folks who are really keen on PR are the Lib Dems, whose power it would massively increase.
And ultimately, the population follows the parties -- unless you are a LibDem supporter you probably don't especially want to see the LibDems holding the balance of power in every parliament for the next fifty years.
