Why are tomboys so accepted?
Simple. Women acquiring male behavior is about power, males acquiring female behavior is deemed to be about sex. The former is acceptable, the latter is considered deviant.
Secondly feminism. This is NOT just about getting equal rights, feminism is primarily about social engineering, getting women to compete/better men by borrowing the "best" bits from masculinity. There is no equivalent masculine movement trying to do this.
Conclusion. Women now live a transgendered lifestyle even if they are not TG themselves as individuals, they have been pushed this way by social forces.