I think our ideas of what class is haven't changed to catch up with reality.
There used to be a big divide between working class jobs (labourers, miners, factory workers etc), and middle class (office jobs, managers, professionals, etc) and being born into one class of people meant you were unlikely to be able to get to the jobs of a different class (a few did).
Now we have much more class mobility, its not uncommon to come from a working class background and get a professional job (and coming from a middle class background is no longer an automatic pass to those jobs, so you get people moving the other way). So either people are always the class they are born in (despite how ridiculous that looks when a hugely wealthy person tries to assure you they are still working class), or they move throughout their lives (in which case the lines become pretty blurred).
And the jobs themselves have changed. Lots of the old working class jobs don't exist, the old middle class jobs have expanded massively, and are now regarded as working class.
Basically, I don't think the class definitions are actually at all useful anymore.
But the rhetoric is far too popular to go away. I.e. stereotypes that the working classes are the only ones who do the real work (traditional middle class jobs like teachers and doctors being just sitting about on your arse eating bon bons, presumably). Or that middle class people are all 'class conscious' and 'keeping up with the Joneses' (which is like nobody middle class I know). Or from the other side the contrasting stereotypes that the hard working middle class families are the backbone of Britain (which is available to all if they would only 'work hard') and the working classes are all chavs and benefit scroungers who exclusively spend money on fags, alcohol and big tvs (again, like nobody working class I know). It's all divide and conquer bollocks.
All the stats on people self identifying as a particular class tells you is which rhetoric is currently 'winning'.