It is a practical way to link an abstract idea to a concrete concept. My experience is that fractions can be understood through the "pie" method but students really understand a fraction when they can see and touch the object in a linear fashion. When the student are able to break the line into smaller parts and physically compare them to a set scale, fractional measurement makes sense. Once the kids have a picture of a fraction and how to use it in measurement the next logical step is a fuller more comprehensive vision of fractions.
In the edugains.ca website, resources section is another quote "Fractions understandings are underpinned by larger mathematics cognitive processes including proportional Foundations to Learning and Teaching Fractions: Addition and Subtraction Page 7 of 53 reasoning (Moss & Case, 1999) and spatial reasoning (Mamolo, Sinclair, Whitely, 2011).
"Fraction and decimal arithmetic are crucial for later mathematics achievement and for ability to succeed in many professions. (Developmental Review, Hugues Lortie-Forgues, Jing Tian, Robert Siegler)