Those are platforms rather than high heels. If you take away the thick sole (ie make it the same thickness as under the instep) and reduce the heel by the same amount, it's not that high relative to current norms.

Also, consider that while platforms were fashionable in the US during the disco era, this is a BBC article. They didn't catch on over in Europe at all. Thinking of 70s movies, I'm not sure that platforms were even that popular outside of the youth culture, and the disco culture at that, whereas high heels are ubiquitous among adult women of all ages except the very old who are unable to wear them in comfort.