Why BU is a mandatory parameter in ESS job of Uninvoiced Receipts Accrual Report

We have a business requirement to run Uninvoiced Receipts Accrual Report for all the BUs. But using the ESS job we can select only one BU at a time. Tried to execute or schedule the report from catalog, but both Open and Schedule options are disabled for this report. We also created copy of the report, but the same properties were inherited.

Can you please let us know why BU is a mandatory parameter in the ESS job of this report?