There are definitely many justifications for implementing PBL into the curriculum.
According to research, PBL lends itself to student achievement through engaging activities that provide collaborative learning skills and improved test scores. Constructivist learning drives PBL.
As Brooks stated:

"Students are given the freedom to think, question, reflect, and interact with ideas, objects and others."

Meaningful learning takes place and students are developing real life skills that are relevant. They are exploring deep into a topic of interest, actively acquiring knowledge. Being a primary teacher, I use PBL in my classroom all the time. Hands-on learning is modeled and encouraged in the primary grades. PBL is great because I am able to reach all of my students' learning styles, and students are motivated to learn.
PBL also has all of the qualities that are necessary to prepare students for 21st Century learning. Students are communicating, thinking critically and making connections.
Understandably, PBL entails a lot of planning by the teacher. Lessons must be developed to meet students needs and interests. Assessments occur through daily classroom projects or activities, and are varied. As teachers, our job is to prepare our students for the future. We should provide learning experiences that foster Pinks "six senses" in order to help our students succeed in an ever changing world. PBL can lend itself to this goal, and enable students to practice the 3C's: Collaborate, Communicate, and Construct knowledge.