But you, equally, seem to believe that state education is ‘better’, so your argument doesn’t hold up as parents are, therefore, not buying advantage, if that is the case.
Perhaps people choose independent schools for options which they believe suit their children - more sport, high-level specialised sports coaching, teaching of Latin, Classics or Music at exam level, a more flexible curriculum? SEND too. Having options should be celebrated.
I would love to see how people who have supported this policy would react if state school places were allocated across a city by a lottery so that buying an expensive property didn’t lead to privileged education by default. There are many types of privilege.