There is no hard and fast rule for where to launch a photography drone, but there are some factors every photographer should consider when picking a spot to launch.
1. Safety of Others. If you are flying in an area crowded with tourists, get as far away from the main parking lot and main attractions as possible. You do not want to have to land in a crowd of people.
2. Think 30 minutes ahead. A parking lot might be empty when you arrive 45 minutes before sunset, but it will probably fill up the closer you get to sunset, and you do not want to have to battle people when landing, or worse, have no room to land where you took off.
3. Think about your line of sight before launching. FAA regulations require that the drone stay in your line of sight. This means that you need to be able to actually see the drone at all times. So, if you have a decent idea ahead of time what you want to shoot, launch in between the furthest points where the drone will go. This maximizes your ability to keep in the line of sight.
4. Be careful of sand, pebbles, and grass. I have seen some DJI promotional videos in which they launch right off of the sand on a beach. Seems pretty risky to me. A few pebbles of sand in the motor could doom a drone. To put it in perspective, consider that a grain of sand relative to a drone motor is probably about the same size as a small rock relative to a 747 jet engine. You wouldn't want a rock sucked into the jet engine, right? So why risk getting sand granules stuck in the drone's motor? Same with pebbles and grass, although grass presents another risk altogether - if your drone's wings start clipping blades of grass, it can deform the wings and leave remnants of the grass on the wing surface. This could alter the drone's aerodynamics later in flight. It is best to launch off of a hard surface free of debris. If you want to, bring a mat with you and you can launch from just about anywhere.
5. Don't Be Seen. If you are not seen, you will not be bothered, and you won't get distracted. Focus is safe. Distraction is unsafe. Drones attract attention, and drone pilots might attract conversation or worse - confrontation. The result can be disastrous during flight. Imagine going into the cockpit and talking the 737 pilot's ear off for the whole flight. It's just not safe, so pick a spot not only where no one is, but also where no one is likely to talk to you during flight, and where you are not seen.