Basically my point is that most people where you could diagnose appendicitis from elevated WBCs followed by ultrasound will probably not be in the hospital or clinic or ED in the first place. The reason this is a surgical emergency is because the symptoms are of rapid onset. Thus, elevated WBCs are of limited utility. Furthermore, because appendicitis is an emergency, ultrasound is not the preferred imaging modality–CT scans are used instead, which are relatively more expensive and expose patients to ionizing radiation.

You can choose to treat patients with antibiotics (and they've done studies), but generally over 50% of patients managed initially with antibiotics will ultimately require surgery anyway within 48 hours, and of the <50% that don't, there is a relatively high recurrence rate that will ultimately also require surgery. Given that appendectomy has a very low morbidity and mortality, this is one of the surgeries that are harder to argue against in my opinion.

From my reading of Uptodate, experts in the field feel similarly; after performing a cost/benefit analysis, initial management with antibiotics is indicated only for patients who cannot undergo surgery.