I think I made a reverse journey. I was brought up in a Mail subscribing household and my mother, as I have said before, thinks the only thing wrong with Thatcher is that she was a bit of a leftie, and I tended towards the right wing even at university. It's since I started doing legal aid work and seeing just how appallingly the most vulnerable people get treated that I moved steadily leftwards.
I always believe this - that the more of society and the world at large you are exposed to, the more left you must rationally become.
As people get older though, it's rare that their world expands. Normally it contracts, as people get married and settle down and move away, most people end up in a steady job and community, surrounded by people in similar situations and with similar lives. Not confronted anymore with any inequality or scarcity, they start to look inwards and become obsessed with petty and trivial grievances and lose all perspective, because there is no longer any comparison, apart from demonised 'others' in the media.
That's why they become right wing, not because they gain any perspective or critical faculties, but because they steadily lose them both as soon as they start to settle.
The mantra that lefties go into such vocations as social work and the arts isn't nessecarilly true by that logic, but just that any open minded educated person couldn't really fail to become left-wing when faced with injustice or new ideas every day.