What if Disney bought Viacom?

Instead of The Walt Disney Company buying 21st Century Fox, why doesn't it buy the rights to Viacom?

Media
Disney will own Viacom's various companies and networks.

Film studios that will be owned by Walt Disney Studios

 * Paramount Pictures
 * Nickelodeon Movies
 * Insurge Pictures
 * Paramount Animation
 * Paramount Players

Television channels and studios that will be owned by Walt Disney Television

 * Paramount Channel
 * Paramount Network
 * Nickelodeon Productions
 * Nickelodeon Animation Studio
 * MTV
 * MTV 2
 * MTV Tr3S
 * MTV Music
 * BET
 * BET Soul
 * BET Jam
 * Nick At Night
 * VH1
 * Comedy Central