Accounting standards notified by central government

It is not clear to me as to why central government had to notify certain Accounting Standards to be followed by auditor while doing audit of companies.

A practicing Chartered Accountant would have any way followed the Accounting Standard issued by ICAI while doing Audit because a practicing member of ICAI is mandatorily required to follow AS issued by ICAI while doing Audit.

Kindly someone give a detailed explanation for this.

Thank you