The reason for the IRS's attendance at both is due to another common guest of both ceremonies - Distinctive Assets. Since 1999 the company Distinctive Assets has put together gift bags which are handed out at both of these ceremonies. Today, the popularity and value of these gift bags has skyrocketed. A gift bag at the Grammys this year is expected to be worth $25,000 and the Oscars gift bag is worth $168,000.
This equates to a big day for taxing authorities. Approximately 121 individuals will receive an Oscars gift bag and approximately 473 individuals will receive a Grammys gift bag. For the IRS and California FTB that equals a $6.26M payday from the Grammys and a $10.73M payday from the Oscars. 
The IRS isn't shy about announcing their presence at these award shows either. Since 2006, the IRS and AMPAS reached an agreement that requires the Academy Awards to include with the gift bags any applicable tax forms as a reminder of the tax due.
The actors and actresses aren't at a total loss; they can follow George Clooney’s footsteps and donate their gift bag to charity and receive a tax deduction for doing so. However, given the amount of income movie and music stars make, it is unlikely they will be able to utilize much of that tax deduction.
 The Grammys give gift bags to all nominees, performers and presenters. While some individuals qualify under multiple categories, it is assumed for this article that there were no duplicates. This equals 473 nominees, performers and presenters. The Oscars give gift bags to all nominees who do not win an Oscar. That equated to 121 individuals last year.