Dosboy's Bits and Bytes

I understand that the Enterprise is on a peaceful mission of exploration, but I'm watching an episode where they're trying to avoid contamination of a pre-warp culture, and in doing so Scott Bakula and British Guy are almost killed. Hot Vulcan stages a rescue operation and they get into a shootout. So, we're talking a shootout between WWII-era weapons and PHASE PISTOLS! And yet the Enterprise crew are all just wearing their cotton jumpsuits. For the love of god, are there no bullet proof vests in the 23rd century?