I've mostly voted LibDem, because for most of my adult life they were the only actually left-wing party. Last election was a definite Labour vote, though, because it seemed very, very important to do whatever was the most likely to not allow the Tories to get in. Not that it made any difference, in this very safe Tory seat, but every little helps as the old woman said when she pissed in the sea.
But it is worth pointing out that there's another reason why many don't vote for the LibDems in recent years - their time in power. More specifically university fees.
Part of that whole thing is the Tories somehow magically managing to make the LibDems' tempering of their worst excesses be, in the public eye, the LibDems being responsible for all the Tories worst excesses. But they had campaigned extensively on tuition fees, so to turn around on it in such a huge way was seen by many as a massive betrayal. I imagine that there's a whole generation of people who were young at the time who then and there decided that they would never vote for the LibDems as long as they lived.
On the plus side, the current generation of young people have lived through the A-levels debacle, and were either forced back in to schools with no help from the government or are now being told that they'll likely have to stay at university over Christmas because it's unsafe for them to go home. So I imagine that's a generation of people who will never vote Tory as long as they shall live.