"We would like to get the chance to get to know new members better and more importantly, we would like for new members to have the opportunity to get to know us better before we fully unleash them on our board."
and
"We have also limited new member's initial membership to ensure they are here for the right reasons. TDH is a Star Wars costuming board that focuses on bounty hunter costuming and even more specifically Boba Fett costuming."
It also helps to protect members from poor quality makers and straight up scammers. By requiring new members to attempt to become part of the community, it discourages unscrupulous sellers by limiting their ability to peddle their wares.
Im also pretty sure the only section new members dont have access to is the cargo hold which is the buy/sell/trade section. So, its exactly as Mike M said
It also protects sellers from people who are bots, scammers etc.... if you invest your time into the site a bit you are less likely to be a threat to the seller also