Because they aren't supposed to be available as 2-stars
There are some 2* champs that were only available in certain event crystals, not the PHC. That's why they show up on the champion list.If I remember correctly, the Doom/FF event had crystals that had 2* champs that aren't in the PHC. Also, last month if you beat the normal EQ you received a 2* Ebony Maw, which is not in the PHC.