The NE part of the Phoenix metro area is also far and away the most affluent (Snottsdale, Paradise Alley, Careless etc.) so the TV stations probably think they would not get enough OTA viewers to make the translator worth the cost.
Also that area has about the lowest population density of the market, so even if it is a quarter of the land area, it is likely only around 15% of the population. If you isolate the area that is to the N or NE of Camelback, it is definitely even less.