The person calling on Thursday wishing to be seen that day may be just as smart as all of the other patients; he may have taken quite ill overnight, and may be in need of urgent care.
While there are appointments that patients can schedule weeks in advance for convenience, they are the rarity in my experience as a patient. I recently needed to see a dermatologist, and it was necessary due to the nature of the condition to see one quickly. I found a practice with a large number of offices, and I made it clear I would gladly travel to all but one of them (an hour's drive was my limit). They accommodated me, and I was very pleased with the physician and his staff-he really listened, and gave me recommendations for treatment. I have since pointed three people toward this doctor.
On the other hand, my rheumatologist seems to feel that his patients have lots of time to spare. He has very limited office hours, and I have yet to see him within 45 minutes of my scheduled time. One hour-and-a-half wait almost sent me over the edge, as it interfered with my job. I tried all the tricks-first appointment, different days- it's always the same. So, while I like this doctor, I'm looking for a new one.
My primary care doctor's practice has a combined access schedule. Each day there are doctors who exclusively see walk-ins. The other practitioners see the scheduled patients, and they don't have to worry about keeping time open on their schedules for emergency patients. A scheduled appointment may take longer than anticipated, but the wait times are still kept to a minimum. Walk-ins are accepted from 8am to 11 pm (with one hour shift change/dinner break at 4) M-F, and from 3-11 pm on Saturday and Sunday. When I go as a walk-in, I know I may have to wait, especially if there's something going around. I'm just grateful for the availability, and I have liked all of the practitioners that have joined this group. Obviously, this won't work for a doctor who is not part of a large group, but it is a good option for a large general practice.