Motive/idea behind enacting new law

Dear Santosh,

The reason for a new act or amendment in an act is given in the form of Statement of Objects and Reasons [i.e. Preamble] prior to the commencement of the sections of the Act.

Hi Santosh!!

To understand the question: why laws are enacted or amended?, you must understand the question why do we need laws? its jurisprudence.

Law has a direct nexus with the society and is an effective tool of maintaining order in the sociey.  The needs of people are ever changing and to meet the everchanging requirements of  the society, laws are either to be enacted or amended.  So the law may be good enough in itself, but to meet the current needs of the society, it has to be updated.

Besides, as said by Mr. Ganesan, you will find the reson in the statement of objects and reasons of every Act.