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:
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.
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.