Alignment and Races

Orcs, Kobolds and Goblinoids were not included in the playable races. These races are created to be evil and their place in adventuring for good is not attainable.
The orcs, kobolds, and goblinoids are inherently evil, created to be so by their gods whether it be Gruumsh or Maglubiyet or Hruugek. An individual would find it very difficult to be of Good alignment because of how closely they are tied to cosmic alignment. Evil is a compulsion on the level of instinct, and it is very hard for any of these creatures to fight that compulsion, let alone defeat it within themselves. At best one of these races, may become benevolent, but they will achieve only a Neutral alignment in regards to the good and evil axis. Exemplars of benevolent humanoids exist like General Vraak of the Zhentarim, or Larktuel the Goblin Cleric. They were able to escape the shadow of evil but they were never able to become Good.
Gnolls are a very similar case to the Orc and goblinkin above but their will is even more tied to alignment. A neutral or Good Gnoll is unheard of.
Some races, though evil, are aligned to evil through an ancient corruption and not due to creationism. Drow, and Duergar are examples of this type of ancestry. Long ago the bloodlines of these races were corrupted by a deity or a force. While still inherently born evil, these creatures can redeem themselves because their race was not created to support an alignment. They were tricked into servitude which lead them to a particular alignment. Good Drow and Duergar are extremely rare, but many notable examples have arisen.