I don't really know why being a mother herself, Marissa Mayer, ended Yahoo's company work at home policy.  I can only speculate that the company might have felt the policy was not helping the productivity of the workers or for some reason the Board of Directors did not think the work at home policy helped the bottom line?  Possibly she might have felt that as a woman her number one priority was still to do what was best for the company as a whole.