Most probably the reason was based on to gain the favor of their bills. They need to have the votes on their bill and because of this, they have to explain it to other members of Congress. They have to be diligent enough to have a popular vote and enact their bill.
Between 1895 and 1898 Cuba and the Philippine Islands revolted against Spain. The Cubans gained independence, but the Filipinos did not. In both instances the intervention of the United States was the culminating event.
