With Nathan being cook, it seemed like he would simply fly under the radar with the housemates deeming him as useful for cooking their meals and therefore not wanting to nominating him. However it looks like the other housemates are annoyed that he wants to have control of the kitchen and what is bought and that they would like an opportunity to cook a few meals. This could make them want to nominate Nathan or in turn have a more shared useage of the kitchen (router?) so that Nathan is no longer the only chef which will make him not as essential as other housemates would have stepped up to the plate to cook.
You can read about Shabby, Josie and John James complaining
here.
He doesnt add anything in terms of for the show and us viewers, so I hope the housemates do something so that there is more of a possibilty he gets put up for eviction!