This is because they wouldn't affect the Pokemon that Traced that Ability. A Gardevoir with Multitype would be hard to get, so they took the option out. Illusion is useless, as you know what Pokemon came out. Flower Gift, I'm guessing, is Cherrim's thing, and Stance Change only works on Pokemon with King's Shield (a total of one Pokemon). Imposter is also impossible to Trace, as the Pokemon copies you before you copy their Ability. Imposter would also make you yourself.
Hope I helped! :D