Why? Because America is not included in this commission and will not have any members on this commission who will attempt to hide the truth. Maybe the truth will reveal that it was America and Israel who were responsible for the 1994 Buenos Aires bombing and not Iran.
U.S.-led coalition conducts 11 airstrikes in Syria, 19 in Iraq against ISIS targets (Reuters)
from the article: U.S. skeptical about Argentina-Iran 'truth commission'