It's for your own safety. Once you do it, you have an assurance that no one can bypass your account nor withdraw your money.

We need to change the password every week to safeguard our trading account from the online fraud.

It is not mandatory but for the security purposes, it is our responsibility to protect our trading account by changing the password weekly.

Some brokers advise their clients to change the passcode weekly to secure account of their customer from any cyberattacks.