Difference Between Reporting Currency & Secondary Ledger

Hello All,

we have one primary ledger & secondary ledger , And only difference is currency.

Primary Ledger currency is INR.

Secondary Ledger currency is USD.

So here only currency is different between primary ledger & secondary ledger. In this case why we cannot use Reporting Currency Function ?

And if it is only currency different already oracle has given reporting currency functionality.

But why again same function given in secondary ledger also ?

Is there any difference ?

Regards

Vijay