There are 341 women already qualified to run at the trials, compared to 181 men.
Realistically, to qualify for the Olympic team, a man needs to run around 2:10, while a woman needs to run around 2:28.
The Men's "B" standard of 2:19 is 7% slower than a reasonably time needed to qualify for the Olympic team.
The Women's "B" standard of 2:45 is 11.5% slower than a reasonable time needed to qualify for the Olympic team.
Moving the standard down to 2:40 would make it 8% slower than a reasonable Olympic qualifying time, and provide more parity with Men's standards.
According to
http://www.marathonguide.com/fitnesscalcs/ageequivalent.cfm
, a men's time of 2:19 is equivalent to around a 2:38 women's time. Conversely, a women's time of 2:45 is equivalent to a 2:25 men's time. Can you imagine how loaded the field would be if the men's "B" standard was 2:25?