Mainly due to legal issues.
As Worldpackers is a global community and provides collaborative travels to all over the world, in order to make sure everyone can travel alone safely and with legal protection, we only allow applications and trip confirmations to people over 18. Worldpackers cannot be responsible for underage people as it does not have the legal background or any insurance to support those people in case something happens.
In any way, you can still save your favorite positions on your wishlist and plan a super birthday trip when you turn 18! <3