you know how after zerg infesting a planet, the protoss bomb the place and kill everything on it? why dont the protoss just do that to char? and all zerg worlds for the matter...
Well... the planets that the Protoss 'Incinerated' were all infested due to the influence of the Terrans and the use of their Zerg Beacons. Char and other main Zerg planets have space defenses, such as Scourge, Mutalisks, and Devourers, to take care of the invading Protoss