And when were those subways built again? The New York subway opened in 1904, the DC metro in 1974, BART (SF Bay Area) in 1972. And the latter two systems were designed for total automation* from the beginning!
And don't say Beijing's opened in 1969, it's technically true but 15/17 lines were built after 2002.
*BART has operators only because of transit union activism and an isolated, pre-opening incident known as the 'Fremont flyer.'