There are a few reasons that might explain it.
First, the situations are more complex. In the past, we didn't fully understand the consequences that wearing the equipment could have on a woman's body, for example.
I began my career in customs, and I wore a bulletproof vest, which fit me quite well, even though I'm a fairly big guy. My wife works in customs as well, and I can tell you that her experience wearing the bulletproof vest isn't the same as mine. It may seem like a trivial thing, but it can cause injuries, which may not have been recognized before.
Oftentimes, the cases are more complex. I won't go through all of them, but I'll give you one example. Last week, I was at a briefing, and it came as a surprise to hear that there were cases involving impacts on reproductive organs. Men can experience those problems as well. For instance, it's pretty clear how post-traumatic stress syndrome could lead to impotence. Women, however, are affected differently, and those effects aren't well known.