Why are so many industries full of women these days?

Jobs like HR, Marketing, even Accounting seem to be full of women these days. Go to almost any office block and room after room will be full of women at computer screens.

Are men simply not applying for these sorts of jobs, or is it more to do with the hiring managers are now mostly misandrist women who see it as their duty to keep straight men out of the work place, so hire mostly women and the occasional gay man and non-white man for diversity?