Because "accepting" it means conceding that it's an unalterable and permanent condition - often times expressed as a biotruth about women being one way and men being another.
Most people feel that isn't the case though. That the disparity is a social problem that we can change and fix.
Recently saw a really interesting well-researched Norwegian documentary that explores this topic and kinda throws that whole view into question:
For the same reason that 50 years ago nobody should have believed that women were less interested in going to college, becoming a doctor, or becoming a lawyer.
All of those are at parity now, but 50 years ago people were spouting opinions just like yours. They were wrong.
it's not 14% of female founders rejected, its 14% of rejected founders were female (while about 13% of accepted founders were female). There's no male persecution going on here.