Dear Manmadha,
To my knowledge, not alone the Factorues Act,1948, no other laws providing for leave benefits to employees require furnishing proper reason for leave applied for. Leave is an employment benefit conferred on the employees primarily for the purposes of rejuvenation of the body and spirit of the employees so as to regain the vigor in the usual process of continuous work and to strike a work-life balance as well and to enable the employees to discharge their social obligations like the other members of the society.
Further, if we analyze the very nomenclatures of the different kinds of leave together with the restrictions imposed on sanction, in my considered opinion, there is no necessity to require the employee to show proper reason while applying for leave and the phrase " proper reason " is a subjective one that cannot be objectively defined to the satisfaction of both the employer and the employee.