Is it, though? Sometime ago, I asked in this thread if anybody could post historical stats that support this theory, which now seems like an objective fact. But any figures I can find are at best mixed. For example the below shows Thatcher won the 18-24 vote easily, and you could hypothesise on the basis of that data that most of the current 60-70 year olds were always right leaning.The idea that, as you get older, you get more Conservative is objectively visible in any series of voting stats you care to check
My own view is that your exposure to politics upon reaching adulthood probably shapes your politics for much of the rest of your life.
https://www.ipsos.com/ipsos-mori/en-uk/how-britain-voted-october-1974