What is the reason for a group exemption?
The IRS states that "Group exemptions are an administrative convenience for both the IRS and organizations with many affiliated organizations." The IRS does not have to process separate applications for each entity in a group and a single letter of exemption is generated for the entire group.
For more information on the group exemption visit the the Internal Revenue Service guide at www.irs.gov/pub/irs-pdf/p4573.pdf .