Shoe trees maintain the shape of your shoes and help revent the toes from curling and the leather from cracking.
Why aromatic cedar? This cedar will absorb the moisture from your shoes (and that's the moisture that can make your shoes smell). Plastic and other wooden shoe trees won't do this - only aromatic cedar shoe trees will.
Also, aromatic cedar has a naturally fresh scent - you won't find it in plastic or any other wooden shoe trees - and that scent will help deodorize your shoes.
Regular use of shoe trees can lengthen the life of your shoes by as much as 30%