In a hospital or healthcare system, all of the doctors can generally see all of the imaging, labs, and notes for all patients. The problem with "curbside consults" -- where another doctor provides an immediate opinion without seeing the patient -- is that 1. The other doctor often doesn't get the full picture without doing a full evaluation. 2. Increased malpractice risk 3. It's not billable.
I'm a doctor, and in my own experience, my first impression from just seeing the images and talking to the other doctor is sometimes completely different from my final opinion after reviewing the chart and seeing the patient.
Wait times are also a problem, because hospitals and clinics like to operate at close to 100% capacity. There are huge fixed costs in a hospital, and hospital profit margins are often <5%, so that's why they have to operate near capacity.