What is the purpose for such structure of kalachuchi?

Answer 1

This flower is also known as frangipani or the Hawaiian lei flower. The scientific name is plumeria acuminata. It grows in tropical climates. The flower smells heavenly to attract insects for pollinating. The leaves are similar to a succulent to retain water. The flowers are large and the wood is weak. This plant will require pruning in winter to help it develop to the right shape to hold the most flowers.

http://hort.ifas.ufl.edu/database/documents/pdf/tree_fact_sheets/pluruba.pdf