A queen mattress is roughly sixty inches by eighty. A 1920s Hollywood courtyard building typically gives you an external stair with a half-landing, a winder at the turn, a door at the bottom that opens outward into the path, and a courtyard walk narrow enough that the planting on both sides touches the mattress as it passes. None of those dimensions were chosen with a modern mattress in mind, and a memory-foam mattress makes it worse rather than better, because it flexes in the middle and refuses to be carried as a rigid panel.
The later stock trades one problem for another. A dingbat or a midrise gives you an internal corridor and an elevator, which sounds easier until the elevator is out, the car is too short for a mattress on the diagonal, or the building requires the elevator to be padded before anything moves. Subterranean garages add a posted clearance that a box truck cannot clear, so the route becomes garage ramp to street on foot.
Then the street. Large stretches of residential Hollywood have no alley, which removes the service access that most of Los Angeles takes for granted. What is left is a frontage under permit parking, street sweeping restrictions that close one side on a given morning, red zones at corners and hydrants, and on the boulevards posted no-stopping hours. A mattress cannot be staged on a public sidewalk while a crew fetches the truck from three blocks away, so the sequencing has to be right first time: truck legally positioned, then carry, then load, then go.
There is also the question of what happens to a mattress left where it should not be. In a multi-family building the trash enclosure is sized and permitted for bins, not for bulky items, and a mattress leaned against it does not become the hauler's responsibility by being there. It becomes the building's problem, and eventually the city's. That is the mechanism behind every mattress you see on a Hollywood alley corner, and it is entirely avoidable.
Finally, condition. We bag mattresses at the door rather than at the truck, and we keep them off the ground on the way out. That is partly courtesy to your neighbors and partly practical: a mattress that has been dragged across a courtyard and a sidewalk arrives in a condition that limits where it can go. If the mattress is one item in a wider move-out, see furniture removal in Hollywood.